Accord des adjectifs (Agreement of adjectives)

Adjectives are describing words which usually accompany a noun(or pronouns) and tell us what someone or something is like:

-une grande vile (a large city)
-un passe-temps intéressant(an interesting pastime)    
-c'etait ennuyeux(its boring)  

In French, adjective agreee in number and gender with the noun or pronoun they refer to. Unlike in English the adjective don't change.French adjective have four different forms which are determined by the noun they go with:

• masculine singular
• feminine singular
• masculine plural
• feminine plural

un passeport vert(a green passport)         une voiture verte(a green car)
des gants verts(green gloves)               des chaussettes vertes(green socks)

Note: If two singular words share the same adjective, the adjective will be in the plural

un foulard et un bonnet rouges(a red scarf and (a red) hat) 

if one of these words is feminine, one masculine, the adjective will be in teh plural:

une robe et un manteau noirs(a black dress and (a black) coat)