a / os 'whether'

Whether: A and Os

Level 4

To report a yes-no question ("She asked if I was ready"), use a + the question form of the verb. Everyday speech often uses os instead.

How It Works

From question to reported question

  • Wyt ti'n barod? → Gofynnodd hi a oeddwn i'n barod. — She asked if I was ready.
  • Fydd hi'n braf? → Dw i ddim yn gwybod a fydd hi'n braf. — I don't know whether it'll be fine.
  • Ddaeth hi? → Wyt ti'n gwybod a ddaeth hi? — Do you know if she came?
  • Oes lle? → Gofynna iddyn nhw a oes lle. — Ask them if there's room.

Everyday speech: os

  • Dw i ddim yn gwybod os ydy hi'n dod. — I don't know if she's coming.
  • Gofynnais i iddi os oedd hi eisiau paned. — I asked her if she wanted a cuppa.

Both are heard in conversation; a is the standard choice in writing.

Ydy, not mae. After a or os, use the question forms: os ydy, a ydy, a oedd. This is the same rule as os (if) — see mae or ydy?.

Questions with a question word just keep that word: Gofynnodd hi ble roeddwn i'n byw (She asked where I lived), Dw i ddim yn gwybod pwy sy'n dod (I don't know who's coming).

Wondering. Tybed works the same way: Tybed a fydd hi'n braf. — I wonder if it'll be fine. See also Reported Speech.

North and South. The North says ydi and o where the South says ydy (or yw) and e: Dw i ddim yn gwybod os ydi o'n dod.

Examples (6)

  1. Gofynnodd y meddyg a oeddwn i'n cysgu'n iawn.

    The doctor asked if I was sleeping well.

  2. Dw i ddim yn gwybod a fydd hi'n braf yfory.

    I don't know whether it'll be fine tomorrow.

    A softens bydd to fydd.

  3. Wyt ti'n gwybod a ddaeth hi i'r gwaith heddiw?

    Do you know if she came to work today?

  4. Dw i ddim yn gwybod os ydy hi'n dod.

    I don't know if she's coming.

    Everyday speech: os, with the question form ydy (ydi in the North).

  5. Gofynnais i iddi os oedd hi eisiau paned.

    I asked her if she wanted a cuppa.

  6. Gofynna iddyn nhw a oes lle i ni.

    Ask them if there's room for us.

Common Mistakes

  • Using the statement form roeddwn after a.

    Gofynnodd hi a roeddwn i'n barod.
    Gofynnodd hi a oeddwn i'n barod.

    A reported question uses the question form of bod: oeddwn, not roeddwn.

  • Using mae after os.

    Dw i ddim yn gwybod os mae hi'n dod.
    Dw i ddim yn gwybod os ydy hi'n dod.

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

How It Connects

Tap a pattern to see what it builds on and what it leads to.

a / os 'whether'Level 4Whether: A and Os

Learn This First

A or os introduce reported yes-no questions.

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Patterns that build on this one.

Words in This Pattern

os