Appendix:Welsh conjugation

There are two sets of rules for conjugating Welsh verbs: one for colloquial Welsh and one for literary Welsh.

Inflection involves adding the required suffix on to the verb stem. For instance, to form the colloquial first-person singular preterite form of yfed to drink, we take the verb stem yf and add on the required ending ais to form yfais.

Colloquial
Colloquial conjugation is much simpler than in literary Welsh: only the preterite, conditional and future tenses, as well as the imperative mood, are built by inflecting the verb stem itself and, even then, all the tenses, as well as the negative imperative (but not the positive), can be formed periphrastically with a conjugated form of an auxiliary verb (,, (in its form ), or ). The passive voice is formed periphrastically with a conjugated form of. Negations are formed by putting after the subject and mutating the conjugating verb a mixed mutation. Letters which undergo an aspirate mutation do so; otherwise a soft mutation occurs (if possible). Example inflections are shown below using the verb.

Imperfective tenses formed with bod yn
The periphrastic conjugation of the imperfective present, imperfect, future, and conditional tenses is in the form of: conjugated form of bod + subject + + verbal noun. The verbal noun does not mutate except for affirmative and interrogative forms after the and  patterns. Negated forms require to follow the subject. The table below shows the relevant colloquial conjugated forms of. Note: some contracted/regional forms have been omitted for conciseness.

Examples:
 * Present:
 * Imperfect:
 * Future:
 * Conditional:

The future and conditional can also be formed inflectionally:
 * Future:
 * Conditional:

Perfective tenses formed with bod wedi
The periphrastic conjugation of the present perfect, pluperfect, future perfect, and conditional perfect tenses is in the form of: conjugated form of bod + subject + + verbal noun. Examples include:


 * Present perfect:
 * Pluperfect:
 * Future perfect:
 * Conditional perfect:

These tenses can be negated either with or with, which triggers soft mutation of the verbal noun and which takes the affirmative form of the verb. Thus can be rephrased as.

Periphrastic preterite and future
The periphrastic conjugation of the preterite is either in the form of conjugated preterite form of gwneud + subject + verbal noun or in the form of ddaru + subject + verbal noun. An alternative periphrastic conjugation of the future is in the form of conjugated future form of gwneud + subject + verbal noun. The verbal noun undergoes soft mutation (if possible). The table below shows the relevant colloquial conjugated forms of ; (used in North Wales) is invariable.

Examples of the preterite with gwneud:

The preterite can also be formed using the invariable form ddaru:

The preterite can also be formed inflectionally:

Examples of the future with gwneud:

Passive with cael
All forms of, both periphrastic and inflectional, can be used to form a construction with passive meaning. The construction is form of cael + subject + possessive determiner agreeing with subject + verbal noun. The relevant inflected forms of cael are:

Examples:

Negative imperative with peidio
The negative imperative (or prohibitive) forms are built as follows: imperative of + â/ag (optional) + verbal noun. The form is used before a consonant (which undergoes aspirate mutation if possible);  is used before a vowel.