The initial consonant sound is usually repeated in two neighbouring words (sometimes also in words that are not next to each other). Alliteration draws attention to the phrase and is often used for emphasis.

Examples: for the greater good of ...; safety and security

Repetition of initial consonant sounds means that only the sound must be the same, not the consonants themselves.

Examples: killer command; fantastic philosophy

If neighbouring words start with the same consonant but have a different initial sound, the words are not alliterated.

Examples: a Canadian child.