One of the very first jobs for an infant is to figure out which sounds are used in the language around them. The world’s languages consist of about 600 consonant sounds and about 200 vowel sounds. Each language only uses a subset of about 40 of these sounds, called phonemes. Phonemes are sounds of a language that distinguish one word from another. For example, /r/ and /l/ are two phonemes in English. “Rake” and “lake” are two English words that differ only in their initial sounds. Each language uses its own unique set of sounds. For example, both /r/ and /l/ are separate phonemes in English, but they are not separate phonemes in Japanese. By simply listening to the language around them, infants learn the set of sounds used by their native language.