When to use yw and when to use mae

Wonder if there’s guidelines about correct grammatical use of yw and mae? Thanks. Quite happy talking about adverbs etc

It all depends on what type of sentence it is.

Identification sentences (i.e. where the first word isn’t the verb) use yw.
Existential sentences (i.e. ones that use “there” in the sentence) use mae in the affirmative and oes & does dim in the interrogative & negative.
Descriptive sentences use mae in the affirmative and yw & dyw in the interrogative & negative.

There are a couple of exceptions (there always are!), but those are the basic guidelines.


Many thanks but not sure which category to put questions starting beth and faint and ble and sut (SW dialect) examples would be great if time allows.

It again depends on the type of sentence.
In an identification sentence, beth is followed by yw - e.g. beth yw’r 'deryn 'na? faint yw bwyd adar?
But if there is a -ing verb after the is/are, it’s not an identification sentence, so you can’t use yw and then it depends on whether the beth/faint is the subject of the sentence or the object.
If they are the subject, they are followed by sy/sydd - e.g. Beth sy’n bwyta’r hadau 'na? Faint sy’n dod i’r ardd bob dydd?
If they are the object, they are followed by mae (with the subject straight after) - e.g. beth mae’r adar yn neud gyda’r brigyn 'na? Faint mae bwyd adar yn costio?

Because ble and sut are generally in the object position, they use mae - e.g. Ble mae’r 'deryn? Sut mae adar yn hedfan?


Diolch yn fawr

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Could you give an example of the use of yw. I only seem to see it in hymns, like Bethlehem Yw!

How about…
Beth yw enw yr emyn?
“Bethlehem Yw” yw enw yr emyn

Maybe it’s just that you’re more used to hearing ydy (yw = ydy).

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Shwmae Siaron. This is an issue that has begun to niggle at me and I know I will worry at it until my brain has securely sorted the concepts. Meantime, it would help me enormously if you would give, say, 3 examples each of identification, existential and descriptive sentences. Dymuniadau gorau. Marie

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Certainly :slight_smile:

Identification sentences:
(an affirmative one) Ci Sion yw hwnna.
(an interrogative one) Ci Sion yw hwnna?
(a negative one) Dim ci Sion yw hwnna.

Existential sentences:
(an affirmative one) Mae petrol yn yr car.
(an interrogative one) Oes petrol yn yr car?
(a negative one) Does dim petrol yn yr car.

Descriptive sentences:
(an affirmative one) Mae’r frechdan 'ma’n flasus.
(an interrogative one) Yw’r frechdan 'ma’n flasus?
(a negative one) Dyw’r frechdan 'ma ddim yn flasus.

Hope that helps.


Diolch, diolch, diolch.

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