Feeling fearful about future events.
The Cambridge Dictionary defines it as "feeling worried about something that you are going to do or that is going to happen." My understanding is that feeling apprehensive is about a future event in particular, meanwhile feeling anxious implies a more prolonged state of worry.
I think most of the time, we are going to use the word "anxious" instead of "apprehensive" by lack of vocabulary. If we can pinpoint the exact kind of nervousness we are feeling, we can put things into perspective and, in the case of "apprehensive", we know that this unpleasant feeling will not last. This example is a reminder that we can expand our awareness by expanding our vocabulary.
Example: I’m very apprehensive about tomorrow’s meeting.
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The size of the cards is 44mm X 67mm (1.73" x 2.64").