Learn Italian: Questo mese è difficile. - This month is difficult.

Nouns ending in -e can be either masculine or feminine. You usually just have to memorize their gender! However, in this sentence, the word questo (this) gives it away. Since questo is masculine, we know mese must be masculine too.

How do I make the word mese plural?

Nouns that end in -e in the singular change their ending to -i in the plural, regardless of whether they are masculine or feminine. So, the plural of mese (month) is mesi (months).

Does the adjective difficile end in -e because mese ends in -e?

No, they just happen to belong to the same word group. The word difficile naturally ends in -e in the singular. These adjectives are the same for both masculine and feminine nouns. For example, if you used a feminine noun like settimana (week), you would still say Questa settimana è difficile.

What happens to difficile if the subject is plural?

Just like nouns in the -e group, adjectives ending in -e change their ending to -i in the plural. To say 'These months are difficult', the whole sentence would change to Questi mesi sono difficili.