Allophone

A phoneme (such as /a/) is an abstract entity under which several different phones (actual speech sounds, such as [ä], [ɐ], [ɑ], [ʌ]) are classified in a speaker's mind. These differing phones are called allophones of one another (or of the phoneme).

There are two subtypes of allophones:

Continuous allophones

The human articulatory organs are not perfect in operation. Since features such as the position of the articulators, intensity of voicing, the (speaker-dependant) shape of the oral cavity, and amount of food stuck between the teeth are continuous variables, any two attempts to articulate a sound will be ever so slightly different from one another. Acoustics of the environment have further effect on the exact sound reaching the ears of an addressee. Yet, the brain processes

There are no special IPA symbols for marking continuous allophones, and the only exact way to record them is a recording of the sound itself; however, for a first approximation, diacritics such as raised/fronted/lowered/backed can be used.