A consonant is a speech sound you make by blocking or restricting the flow of air through your mouth in some way. When you say the letter B, your lips press together and then pop apart. When you say S, you force air through a narrow gap between your tongue and the roof of your mouth. When you say M, you close your lips and let the sound come out through your nose. All of these are consonants.

Most consonants need to pair up with vowels (A, E, I, O, U) to make words, because consonants by themselves can be hard to pronounce or hear clearly. Try saying “strength” slowly and you'll notice how the consonants (S, T, R, N, G, TH) wrap around the single vowel sound in the middle.

The word consonant can also mean “in agreement with” or “matching up with something.” If your actions are consonant with your words, you're doing what you said you would do. A student whose careful work is consonant with their ambition to become a scientist shows that their behavior matches their goals.