Lesson 21 deals with the past tense of the eleven irregular verbs.

As the title suggests, irregular verbs do not follow regular patterns, or
may vary a great deal in form from tense to tense.

We dealt with past tense regular verbs in lesson 13 (and a few irregular
ones as well). Some of the features of past tense verbs you learnt in
lesson 13 will apply to irregular verbs in the past tense; some will not.
It's best to learn the irregular verbs separately -- separate from regular
verbs and separate from one another.

Apart from these verb forms, no new grammar is introduced, so let us
conclude with these irregular verbs, fully conjugated:

bhí mé, bhí tú, bhí sé, bhí sí, bhíomar, bhí sibh, bhí siad
chonaic mé, chonaic tú, chonaic sé, chonaic sí, chonaiceamar, chonaic
sibh, chonaic siad
chuala mé, chuala tú, chuala sé, chuala sí, chualamar, chuala sibh, chuala
siad
rinne mé, rinne tú, rinne sé, rinne sí, rinneamar, rinne sibh, rinne siad
thug mé, thug tú, thug sé, thug sí, thugamar, thug sibh, thug siad
tháinig mé, tháinig tú, tháinig sé, tháinig sí, thángamar, tháinig sibh,
tháinig siad
rug mé ar, rug tú ar, rug sé ar, rug sí ar, rugamar ar, rug sibh ar, rug
siad ar
fuair mé, fuair tú, fuair sé, fuair sí, fuaireamar, fuair sibh, fuair siad
d'ith mé, d'ith tú, d'ith sé, d'ith sí, d'itheamar, d'ith sibh, d'ith siad
dúirt mé, dúirt tú, dúirt sé, dúirt sí, dúramar, dúirt sibh, dúirt siad
chuaigh mé, chuaigh tú, chuaigh sé, chuaigh sí, chuamar, chuaigh sibh,
chuaigh siad

Negative and interrogative forms of the same will be introduced next lesson.