N4
よていだ
Plan to, Intend to
今夜は先輩たちと飲みに行く予定だ。
I plan to go drink with some of the senior staff tonight.
Explanation
「〜予定だ」 means 'be scheduled to' or 'plan to'. It speaks of a schedule or plan already arranged and decided. It can be yours or someone else's, or a company's: 「新幹線は10時に到着する予定です」 (The Shinkansen is due to arrive at ten). After a noun use 「の」: 「出張の予定です」.
Mixed up with
Levels of plans: 「〜と思う」 is a thought that just came up; 「〜つもりだ」 is your firm intention, not necessarily on the calendar; 「〜予定だ」 is a fixed schedule, often involving others; 「〜ことになる」 is decided by an organization or other people.
If the plan later changed, use the past: 「〜予定でした」, 「〜予定だったが……」.