Phonology is the study of the organization and use of sounds in natural languages. Phonologists describe and categorize the sounds of speech using the international phonetic alphabet, a system of symbols used to unambiguously represent individual speech sounds in all the world's languages.
Terms used in phonology
A phoneme is the smallest unit of sound whose change can change the meaning of what is said.
A minimal pair is a pair of words that differ by only one phoneme, e.g., hit and hid. The existence or not of a minimal pair tests whether two apparently different sounds are actually phonemes.
An allophone (from Greek "other" and "sound") is an audibly distinct sound that is not a separate phoneme. Examples are the aspirated initial p and unaspirated final p of pip. In English, there is no minimal pair, while in some languages, such as Mandarin Chinese, there could be, in which case those two sounds would be phonemes, not allophones.
Tone is the use of pitch to distinguish words. Different tones that distinguish words in the same way as phonemes are called tonemes, and languages with tonemes are called tonal languages. The majority of languages in the world are tonal languages.