Nouns - Gender

In English he or she is used for people and it for things. But there are some exeptions.

male (masculine)	female (feminine)
brother	sister
nephew	niece
boyfriend	girlfriend
actor	actress
waiter	waitress

There are nouns which have the same form for masculine and feminine, e.g. cousin, doctor, singer, student, teacher.
An extra word identifies the gender - boyfriend/girlfriend.
The ending -ess indicates a female person - waiter/waitress.

Execptions:

1) Animals

If you know the gender of an animal, you can use he/she for it.

Where is the cat? She is in the garden.

2) Ships, cars, countries

For ships, cars and countries (when referred to by name) the feminine form is sometimes used, but this is rather obsolete. There is a tendency to use it instead of she.

The Titanic was a great ship, but she hit an iceberg and sank.