Feminine nouns ending in '-o'
When you first learn Italian, one of the most reliable rules is that nouns ending in -o are masculine. Words like il libro and il gatto follow this pattern perfectly. However, you will soon encounter a small but very important group of everyday words that end in -o but are actually feminine.
If you treat these exceptions as masculine, you will use the wrong articles and adjectives. For instance, saying il mio foto instead of the correct la mia foto is a common beginner mistake. Let us look at why these words exist and how to use them correctly.
Many feminine nouns ending in -o are simply abbreviations of longer feminine words. Because they are shortened versions, they keep the feminine gender of the original word. For example, foto is short for fotografia, auto is short for automobile, and moto is short for motocicletta. Metro comes from metropolitana.
There is a great bonus to these abbreviations. When you make them plural, the ending does not change to -i. The noun stays exactly the same. To talk about more than one, you only change the article or adjective before the noun, such as moving from la to le.
Not all feminine words ending in -o are abbreviations. The most common exception you will use is mano (hand). It is a feminine noun, so you say la mano, la mia mano, or una mano.
Unlike the abbreviations we just looked at, mano does change its ending in the plural. It follows the regular Italian plural rule for feminine words, shifting to an -i to become le mani (the hands).
A noun ending in -o is usually masculine, but a few essential words break the rule. Most of these, like la foto and l'auto, are short for longer feminine words and do not change their spelling in the plural. The major exception is la mano, which is feminine but changes to le mani in the plural. Always learn these nouns with their feminine articles to build a strong habit.