mae or ydy?

Level 3

Both mae and ydy mean "is". Mae is the everyday statement form; ydy (yw in the South, ydi in the North) is used in a few special places.

How It Works

Use mae:

  • in statements: Mae hi'n oer, Mae'r plant yn chwarae
  • after ble, sut, pryd, pam: Ble mae'r banc?, Sut mae'r tywydd?, Pam mae hi'n crio?
  • after beth when beth is the object: Beth mae hi'n (ei) wneud? (What is she doing?)

Use ydy (yw, ydi):

  • in yes-no questions: Ydy hi'n oer?, Ydy'r caffi ar agor?
  • in negatives: Dydy hi ddim yn oer (South Dyw hi ddim)
  • after os (if): Os ydy hi'n braf...; see os
  • after a word moved to the front: Meddyg ydy hi; see athro dw i
  • when identifying with a definite noun or asking what or who: Siân ydy'r athrawes, Beth ydy hwn?, Pwy ydy hi?, Faint ydy e?

Two more partners. For "Is there a...?" with an indefinite noun, use oes: Oes caffi yma? (see oes and does dim). When who or what is the subject, use sy: Pwy sy'n dod? (see pwy sy and beth sy).

The regional forms yw and ydi are explained in ydy yw and ydi.

Examples (6)

  1. Ble mae'r swyddfa bost?

    Where's the post office?

    Ble is followed by mae.

  2. Ydy hi'n bwrw glaw eto?

    Is it raining again?

    Yes-no question: ydy.

  3. Dydy hi ddim yn oer.

    It isn't cold.

    Negative: dydy. South: Dyw hi ddim yn oer.

  4. Os ydy hi'n braf, awn ni allan.

    If it's fine, we'll go out.

    After os: ydy, not mae.

  5. Nyrs ydy hi.

    She's a nurse.

    The job is moved to the front, so the verb is ydy.

  6. Siân ydy'r athrawes.

    Siân is the teacher.

    Identifying one definite person with another: ydy.

Common Mistakes

  • Using mae after os.

    Os mae hi'n braf, awn ni allan.
    Os ydy hi'n braf, awn ni allan.

    After os (if), the present of bod is ydy (yw), not mae.

  • Using ydy after ble.

    Ble ydy'r orsaf?
    Ble mae'r orsaf?

    Ble, sut, pryd and pam are followed by mae.

How It Connects

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mae or ydy?Level 3

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Choosing mae or ydy compares statements with questions, negatives and identifying sentences.

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