Passed is the past tense of the verb ‘to pass’. It’s used to describe things that have already happened. It’s also the past participle of ‘to pass’ so it’s used for the passive voice (the law was passed) and perfect tenses (thirty years have passed by so quickly).
Passed is only ever a verb form.
Past, however, has lots of different functions – it is an adjective, a noun and a preposition.
As a noun:
- The time before the present moment (we didn’t use that method in the past)
- The history of a place or person (he never talks about his past)
As an adjective:
- Gone by in time or no longer existing (his best years are past)
- Happening before and leading up to the time of speaking or writing (he’s really grown in the past year)
As a preposition:
- From one side of something to the other (he ran past her and into the house)
- Telling the time (it’s past midnight)
- Further than a specific point (I can see past the harbour and out over the sea)
As an adverb:
- To move from one side so as to move from one side of something or someone to the other (she saw a car going past)
- time going by (a year went past before she saw him again)