ー予定がある/ない

予定 means 'plan', and it is a noun. To express, "I have a plan to do such and such," you can use the following pattern:

[Sentence....(Plain Form of a Predicate)]予定がある。

Consider the following sentences:

-予定です is also used to express one's plan, and it corresponds to English, "I am planning to do such and such".

You can also express your plan by using つもり. The difference between 予定 and つもり is that 予定 expresses a plan that has been arranged/scheduled in advance whereas つもり expresses one's immediate/spontaneous plan.

Naturally, 予定 expresses a more serious plan than つもり.

Compare, for instance, the following:

However, in many cases, 予定 and つもり can be used interchangeably.