What is the meaning of the word "part"?

Definitions:

a line of scalp that can be seen when sections of hair are combed in opposite directions noun
- Their part was right in the middle.
a portion of a natural object noun
- they analyzed the river into three parts
an actor's portrayal of someone in a play noun
- I played the part of Desdemona in a local play.
go one's own way verb
- move apart
one of the portions into which something is regarded as divided and which together constitute a whole noun
- the written part of the exam
something determined in relation to something that includes it noun
- They wanted to feel a part of something bigger than themselves.
something less than the whole of a human artifact noun
- the rear part of the house
that which concerns a person with regard to a particular role or situation noun
- it requires vigilance on our part
the melody carried by a particular voice or instrument in polyphonic music noun
- I tried to sing the tenor part.