The term 'Unit of Speech' can refer to two different concepts. The first is a phoneme, which is the smallest unit of sound in a language that can distinguish one word from another. For example, the phonemes /p/ and /b/ are distinct units of sound that can differentiate between the words 'PAT' and 'BAT'. The second concept is a toneme, which is a unit of pitch or intonation used to convey meaning in some languages. For example, in Mandarin Chinese, the same syllable can have different meanings depending on the toneme used.