Why does conscio not have four principal parts?

The short answer is, it means that form is never attested. The authors of the dictionary have never seen a form of consciō using its fourth principal part.

1. What are the 4 principle parts in Latin?
2. What are the four principal parts of a verb?
3. Why are some Latin verbs irregular?

What are the 4 principle parts in Latin?

In Latin grammar: the two principal parts of a noun are the singular nominative and the singular genitive; the three of an adjective are the masculine, the feminine, and the neuter singular nominatives; and the four of a verb are the first-person singular present active indicative, the 1st-pers.

What are the four principal parts of a verb?

1: A verb has four principal parts: the present, the present participle, the past, and the past participle. The first principal part, called the present, is the form of a verb that is listed in a dictionary.

Why are some Latin verbs irregular?

Several verbs add some of the personal endings of the present system directly to the root,¹ or combine two verbs in their inflection. These are called Irregular Verbs. They are sum, volō, ferō, edō, dō, eō, queō, fīō, and their compounds.