In music, flat means "lower in pitch by a semitone," and has an associated symbol, which looks like a lowercase "b"; the note A flat is shown in musical notation in Figure 1. Under equal temperament, C flat is the same as B and F flat is the same as E. There also exist double-flats, which look roughly like "bb".

In musical tuning, flat can also mean "very slightly lower in pitch." If two strings are slightly out of tune, the lower-pitched one is said to be flat with respect to the other.

Figure 1. The note A flat on the treble clef.

See also sharp

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The word flat also has other, unrelated uses:

• flatness
• flat tire
• flat tax
• flatline
• A flat is another name for an apartment
• In abstract algebra, a module is flat if taking the tensor product with it preserves exact sequences.