Is the word forest masculine or feminine?

Answer 1

In English there are no masculine or feminine forms. English uses gender specific nouns for a male or a female, such as male and female. Nouns that can be either a male or a female, such as parent, are common gender nouns; nouns for things that have no gender are neuter.

If you are writing poetically, it is a matter of choice. Normally, it is treated as neuter.

Answer 2

That depends on the language. In English nouns have no gender and are neither masculine or feminine. In French, it is feminine (la forêt). In Spanish, it is masculine (el bosque). In Arabic, it is feminine (al-ghaaba / الغابة).