<b>hamjensbâz</b> -> <b>ham</b>: homo (as you see, they're cognate
); <b>jens</b>: sex (cognate with genus
); <b>bâz</b>: present stem of <b>bâxtan</b>: to play, to engage onself in. So it means: someone who practices (engaged in) homosexuality
<b>hamjensga/erâ</b> -> <b>ga/erâ</b>: present stem of <b>ga/erâyidan</b>: to be inclined, to have a tendency. So it means: someone who has a tendency toward homosexuality.
<b>hamjensbâz</b> is not a derogatory word. it is used in newspapers, etc. (I mean in bookish Persian). <b>hamjensgarâ</b> is more formal but anyway it's not used in spoken Persian.
bâz is a productive suffix in colloquial Persian. Look at these words:
<b>baccebâz</b> - pederast
<b>zanbâz</b> - a man who has / is inclined to have relationship with several women / girls <b><i>(what do you say in English? Don Juan?)</i></b>
<b>doxtarbâz</b> - a boy who has / is inclined to have relationship with several girls (one who has several girlfriends) <b><i>(what do you say in English?)</i></b>
<b>pesarbâz</b> - ditto but for a girl <b><i>(what do you say in English?)</i></b>
If you add -i you get the nominal form e.g.
baccebâzi means pederasty.
I think the English for <b>evâ xâhar</b> is "sissy". <b>evâ xâhar</b> means "a boy who behaves in a girlish manner". one who is <b>evâ xâhar</b> is not necessarily a homosexual. he just behaves in a girlish manner, may dress like a girl, may clean his eyebrows (it's taboo in our culture even though many of actors do it), may use feminin cosmetics (rouge, etc.), etc. In short, one who lacks stereotypically masculine qualities. evâ xâhar, literally means "oh, sister". evâ is an exclamatory word used by women.