In Welsh grammar, the conditionals theory refers to the study of sentences that express hypothetical or uncertain situations. There are three main types of conditionals: present hypotheticals, past hypotheticals, and future hypotheticals.

Present hypotheticals, also known as first conditional, express a condition that is likely to happen in the present or future, and the result or consequence that will follow. For example, “Mae eisiau i mi fynd am dro os yw hi’n bwrw glaw” (I will go for a walk if it is raining).

Past hypotheticals, also known as second conditional, describe a situation that is not likely to happen in the present or future, and the result or consequence that would follow if it did. For example, “Byddwn i’n hapus pe bai’n gallu dod am dro” (I would be happy if I could go for a walk).

Future hypotheticals, also known as third conditional, express a hypothetical situation in the past and the result or consequence that would have followed if it had happened. For example, “Byddwn i wedi bod yn hapus pe bai wedi gallu mynd am dro” (I would have been happy if I had been able to go for a walk).