French adjectives agree with the noun they describe. To make an adjective feminine, add -e (grand, grande); to make it plural, add -s (grands, grandes). If it already ends in -e, the feminine looks the same (jeune, drôle), and sympa never changes in gender. Some are irregular: beau/belle, vieux/vieille, gentil/gentille. The -s and the final -e are often silent in speech, except that the feminine makes the last consonant audible: grand /grã/, grande /grãd/.

Position: most adjectives go after the noun (un garçon sympa, une femme brune). A small group of very common adjectives go before it: petit, grand, jeune, vieux, beau, joli, bon, mauvais (think of beauty, age, goodness and size). So un petit garçon, une belle femme, un jeune homme.

An English speaker will often put the adjective in front of the noun every time or forget to make it agree. Check the gender of the noun first, then add the -e or -s.