Basic Conditional Sentences in Welsh

In Brief

Use os for a real or open condition: something that may happen, regularly happens, or is currently true. For a possible future event, Welsh commonly uses a future form in the os clause as well as in the result: Os bydd hi'n braf, byddwn ni'n mynd (“If it is fine, we will go”). This differs from English, which normally avoids will directly after if.

Overview

A conditional sentence connects a condition with its consequence. The condition is the if-clause—the part beginning with “if”—and the other clause gives the result. In Os bydd hi'n braf, af i am dro, the weather being fine is the condition, and going for a walk is the possible result.

At B1, the main Welsh word you need for real and possible conditions is os, “if.” These are often called open conditions, because the speaker is not presenting the condition as imaginary or impossible. You can use them for plans, warnings, offers, instructions, habits, and facts.

The biggest adjustment for an English-speaking learner concerns tense. English normally says “If it is fine, I will go,” not “If it will be fine.” Welsh, however, commonly puts future bod (“to be”) in the condition: Os bydd hi'n braf, af i. Present-tense forms also occur, especially when the condition concerns what is true now, an existing plan, or a general truth.

How It Works

The two-clause pattern

The basic order is:

Part	Welsh pattern	Meaning
Condition first	Os + condition, result	If X, then Y
Result first	Result os + condition	Y if X

Welsh does not require a separate word meaning “then.” Compare:

• Os bydd hi'n braf, byddwn ni'n mynd. — If it is fine, we will go.
• Byddwn ni'n mynd os bydd hi'n braf. — We will go if it is fine.

The meaning is essentially the same. A comma is natural when the longer os clause comes first; it is usually unnecessary when that clause comes last.

Open future conditions: os + future

For a genuinely future possibility, a reliable B1 pattern is:

Os + future form, future result

The future of bod acts as an auxiliary (a helping verb). It combines with yn and a verb-noun—the basic dictionary form used for an action—to express what someone will do:

• byddi di'n gweithio — you will work
• byddwn ni'n aros — we will wait
• byddan nhw'n dod — they will come

It can also introduce a state or description:

• bydd hi'n braf — it will be fine
• byddi di'n barod — you will be ready
• bydd y siop ar agor — the shop will be open

Useful common spoken forms are:

Person	Future of bod	Example in a condition
I	bydda i	os bydda i'n gorffen — if I finish
you, singular familiar	byddi di	os byddi di'n dod — if you come
he / she / it	bydd e / hi	os bydd hi'n braf — if it is fine
we	byddwn ni	os byddwn ni'n aros — if we stay
you, plural or polite	byddwch chi	os byddwch chi'n barod — if you are ready
they	byddan nhw	os byddan nhw'n cytuno — if they agree

The result clause does not have to repeat bydd. Welsh also has inflected, or short, future verbs whose endings show the person:

• af i — I will go
• awn ni — we will go
• arhoswn ni — we will stay

That gives two natural-looking types of result:

• Os bydd hi'n braf, bydda i'n mynd am dro.
• Os bydd hi'n braf, af i am dro.

Both mean “If it is fine, I will go for a walk.” The second uses the short future of mynd, “to go.” You do not need to convert every result into a short form before using conditionals confidently; future bod + yn + verb-noun is a productive pattern.

Present conditions

Use a present form when the condition is about the current situation, a present arrangement, or something generally true. The sentence supplied in the core concept illustrates a current arrangement:

• Os wyt ti'n dod, dere'n gynnar. — If you are coming, come early.

Here wyt ti'n dod asks us to accept “you are coming” as the present situation or plan. The result is a command, not a future statement.

Common present forms after os include:

Function	Welsh	Example
I am	os ydw i...	os ydw i'n iawn... — if I am right...
you are	os wyt ti...	os wyt ti'n dod... — if you are coming...
he/she/it is	os yw...	os yw'r drws ar gau... — if the door is closed...
we/they are	os ydyn...	os ydyn nhw gartref... — if they are at home...
there is/are	os oes...	os oes amser... — if there is time...

For repeated facts, both clauses can be in the present:

• Os yw dŵr yn rhewi, mae'n troi'n iâ. — If water freezes, it turns into ice.
• Os oes gormod o draffig, mae'r bws yn hwyr. — If there is too much traffic, the bus is late.

English speakers should not reduce the distinction to “Welsh always uses the future after os.” Future bydd is characteristic of an open future condition; present forms remain useful when the speaker is describing a current or regular relationship.

The result can be more than a future statement

The result clause expresses what follows from the condition. It may therefore contain:

• a future: Os bydd hi'n braf, awn ni allan. — If it is fine, we will go out.
• a command: Os wyt ti'n dod, dere'n gynnar. — If you are coming, come early.
• permission or ability: Os byddwch chi'n gorffen, gallwch chi fynd adref. — If you finish, you can go home.
• advice or necessity: Os byddi di'n sâl, rhaid i ti aros gartref. — If you are ill, you must stay at home.
• a present result: Os oes problem, dw i yma. — If there is a problem, I am here.

Choose the result according to your intended meaning; do not insert a future merely because the sentence contains os.

Negative conditions: os na and os nad

To make the condition negative, use os na or os nad, rather than placing ordinary ddim after the verb. Before future bod, na causes the initial b to soften to f:

• os byddi di... — if you will be...
• os na fyddi di... — if you will not be...

Before certain present forms beginning with a vowel, you will meet nad:

• os nad yw... — if it is not...
• os nad oes... — if there is not...

The most useful negative frames to learn as whole units are os na fydd..., os nad yw..., and os nad oes....

Examples in Context

Welsh	English	Note
Os bydd hi'n braf, af i am dro.	If it is fine, I will go for a walk.	Future condition; short future af i in the result.
Os bydd y trên yn hwyr, bydda i'n ffonio.	If the train is late, I will phone.	Future bydd appears in both clauses.
Byddwn ni'n bwyta yn yr ardd os bydd hi'n gynnes.	We will eat in the garden if it is warm.	The result comes first.
Os byddan nhw'n cytuno, bydd y cyfarfod ddydd Llun.	If they agree, the meeting will be on Monday.	A realistic future arrangement.
Os wyt ti'n dod, dere'n gynnar.	If you are coming, come early.	Present arrangement followed by a singular command.
Os yw'r drws ar gau, defnyddiwch y drws cefn.	If the door is closed, use the back door.	Present condition followed by a polite/plural command.
Os oes gen ti amser, helpa fi gyda hyn.	If you have time, help me with this.	Literally uses the Welsh “there is time with you” pattern.
Os oes gormod o draffig, mae'r bws yn hwyr.	If there is too much traffic, the bus is late.	A regular consequence in the present.
Os na fyddi di'n barod, awn ni hebddo ti.	If you are not ready, we will go without you.	Negative future condition from the core concept.
Os na fydd y siop ar agor, byddwn ni'n dod yn ôl yfory.	If the shop is not open, we will come back tomorrow.	na fydd makes the future condition negative.
Os nad oes digon o amser, gallwn ni orffen yfory.	If there is not enough time, we can finish tomorrow.	Negative existential condition: nad oes.
Os nad yw'r ateb yn gywir, rho gynnig arall arni.	If the answer is not correct, have another try.	Negative present condition followed by advice.
Beth wnawn ni os bydd hi'n bwrw glaw?	What will we do if it rains?	The conditional is inside a question.

Common Mistakes

Copying the English present tense into every future condition

• Less reliable for the intended future meaning: Os yw hi'n braf yfory, byddwn ni'n mynd.
• Better: Os bydd hi'n braf yfory, byddwn ni'n mynd.
• Why: For an open future possibility, Welsh commonly uses future bydd in the os clause. English “If it is fine tomorrow” can hide this difference.

Adding ordinary ddim to a negative os-clause

• Wrong: Os byddi di ddim yn barod...
• Right: Os na fyddi di'n barod...
• Why: A negative condition uses the negative linking particle na/nad. With future bod, bydd is softened to fydd.

Using a question form because the outcome is uncertain

• Wrong: Os fydd hi'n braf, awn ni allan.
• Right: Os bydd hi'n braf, awn ni allan.
• Why: An if-clause expresses uncertainty, but it is not grammatically a direct question. Use affirmative bydd, not interrogative fydd, after affirmative os.

Forcing future tense into a command or general truth

• Awkward for a current plan: Os byddi di'n dod, byddi di'n dod yn gynnar.
• Natural: Os wyt ti'n dod, dere'n gynnar.
• Why: The condition concerns an existing plan, and the result is an instruction. The tenses and moods should reflect those meanings rather than follow one rigid formula.

Confusing a real possibility with an imaginary situation

• Wrong for an ordinary weather plan: Pe bai hi'n braf yfory, awn ni am dro.
• Better: Os bydd hi'n braf yfory, awn ni am dro.
• Why: Os leaves tomorrow's weather open. Pe normally introduces a more remote, imagined, or contrary-to-fact condition and belongs to a more advanced pattern.

Usage Notes

In everyday Welsh, you will hear regional differences in forms of bod, pronouns, and short verbs. For example, southern speech often uses e for “he,” while northern speech commonly uses o. The conditional framework remains recognizable: os introduces a real/open condition, and future bod is common when that condition points ahead.

The spoken forms bydda i and byddan nhw coexist with more formal written forms such as byddaf and byddant. Use the variety taught in your course or used by your community, but learn to recognize both. Mixing a normal spoken form with a clear os pattern is not a grammatical failure.

Commands also vary by person. Dere'n gynnar addresses one familiar person; dewch yn gynnar addresses several people or can sound more polite. This distinction belongs to the result clause, not to os itself.

Finally, English translations often use a present tense where Welsh uses a future: os bydd hi'n braf is naturally translated “if it is fine,” not usually “if it will be fine.” Translate the meaning of the whole construction rather than matching each tense mechanically.

Beyond the Basics / Advanced Use

Os versus pe

The basic contrast is between an open condition and a remote or imagined one:

Speaker's view	Typical Welsh opener	Example
Real, possible, or generally true	os	Os bydd gen i amser, af i. — If I have time, I will go.
Imagined, unlikely, or contrary to fact	pe	Pe bai gen i fwy o amser, byddwn i'n teithio. — If I had more time, I would travel.

The pe bai... byddwn... pattern introduces conditional verb forms and deserves separate study. At this stage, the practical rule is simple: use os for a plan whose condition may genuinely be met; do not use pe merely because English happens to use the word if.

Mixed time references

The two clauses do not have to refer to exactly the same time. A present fact can determine a future decision:

• Os yw'r ffordd ar gau nawr, byddwn ni'n mynd ffordd arall. — If the road is closed now, we will go another way.

A future event can also trigger a command:

• Os bydd y meddyg yn ffonio, dywed wrthi fy mod i allan. — If the doctor phones, tell her that I am out.

This is why it is better to think in terms of meaning—current fact, open future, command, result—than to memorize “future plus future” as an unbreakable equation.

Focus and clause order

Putting the os clause first makes the condition the frame for what follows. Putting it last often gives the result more prominence:

• Os bydd popeth yn iawn, byddwn ni yno erbyn chwech. — The condition sets up the promise.
• Byddwn ni yno erbyn chwech os bydd popeth yn iawn. — The expected arrival receives the emphasis, with a qualification added afterward.

This is a matter of information flow, not a change in the basic conditional meaning.

Practice Tips

1. Build paired sentences. Start with a future statement such as Byddi di'n gorffen yn gynnar and turn it into a condition: Os byddi di'n gorffen yn gynnar... Then add a realistic result.
2. Contrast English and Welsh aloud. Say “If it is fine, we will go,” then Os bydd hi'n braf, byddwn ni'n mynd. Deliberately noticing the future in the Welsh os clause helps prevent English tense habits from taking over.
3. Drill three negative frames. Make one daily example with each of os na fydd, os nad yw, and os nad oes. Learning these as chunks is easier than rebuilding the negative grammar every time.

Related Concepts

• Prerequisite: Bod – Future Tense — supplies the forms of bydd used in open future conditions and results.
• Next step: Conditional Mood — learn forms such as baswn i and how Welsh expresses what someone “would” do in imagined situations.
• Next step: Temporal Clauses — compare os (“if”) with time linkers such as pan (“when”), where the speaker presents the event differently.