This is the 560th most frequent Turkish word.
açan
"One who opens" or "that which opens."
In this sentence, 'açan' is part of the phrase 'çiçek açan', which describes the tree as one that is blooming flowers. 'Açan' functions as an active participle derived from the verb 'açmak' (to open or to bloom).
Bahçede çiçek açan bir ağaç var.
In the garden, there is a tree that is blooming flowers.
Here, 'açan' refers to the person who performed the action of opening the door. It is used as an active participle to describe the doer of the action expressed by the verb 'açmak'.
Kapıyı açan kimdi?
Who opened the door?
In this sentence, 'açan' modifies 'çiçekler' (flowers), describing them as the ones that bloom seeing the sunlight. Again, 'açan' serves as an active participle.