Participle present. Doing.
Participle preterit. Done.
Do is sometimes used superfluously, as I do love, I did love; simply for I love, or I loved; but this is considered as a vitious mode of speech.
It is sometimes used emphatically; as,
I do love thee, and when I love thee not,
Chaos is come again. Shakespeare.
It is frequently joined with a negative; as, I like her, but I do not love her; I wished him success, but did not help him. This, by custom at least, appears more easy than the other form of expressing the same sense by a negative adverb after the verb, I like her, but love her not.
The imperative prohibitory is seldom applied in the second person, at least in prose, without the word do; as, Stop him, but do not hurt him; Praise beauty, but do not dote on it.
Its chief use is in interrogative forms of speech, in which it is used through all the persons; as, Do I live? Dost thou strike me? Do they rebel? Did I complain? Didst thou love her? Did she die? So likewise in negative interrogations; Do I not yet grieve? Did she not die?