have not yet
Describes an action or state that has not happened yet, with an implication that it is expected to happen later.
This pattern expresses that something has not yet occurred, often with the nuance that it will eventually. It's the polite negative present perfect. For example, if you haven't eaten breakfast yet, you say まだ朝ごはんを食べていません. The 'まだ' (still\/yet) emphasizes the not-yet aspect. In casual speech, you might hear まだ〜てない, but the polite form is 〜ていません. Note that this is a state, not an action in progress, so it's not used for things like 'I am not eating' (that would be 食べていません without まだ, but it could also mean that).