Unlike phonemes, allophones do not create distinctions in meaning between one word and another. They are variant ways of articulating the same phoneme. That is to say, they are predictable phonetic variants.
Phonemes are the basic unit of speech. They are the simplest speech sounds that are used to differentiate between one word and another. A phoneme is capable of creating distinctions in meaning between words.
Vowels are open sounds, produced with the vocal cords vibrating and with no obstruction to the airflow from the lungs. There are approximately 20 vowels in British English.
Phonetics studies articulation, i.e. how the sounds of particular languages are articulated in particular contexts. This article explains the articulation of the 24 English consonants. They are categorized as either plosives, nasals, fricatives, affricates or approximants.
Phonology is the study of the rule system that governs how particular speech sounds are used to produce meaningful words. It investigates the systematic organization of sounds in a particular language. It describes the basic units of speech in any language and examines how speech sounds change when they are combined.
Phonetics is the study of speech sounds. It investigates the physical properties of speech sounds, how they are produced by the vocal tract, and how people perceive these sounds. The field is typically divided into three areas: acoustic phonetics, auditory phonetics, and articulatory phonetics. Speech therapists are particularly concerned with articulatory phonetics.
Speech is the primary transmission system of language. It is divided into two subcategories: phonetics and phonology. Phonetics studies the physical properties of speech sounds and how they are produced and perceived. In contrast, phonology examines the rules which govern how sounds are organized and combined to create meaningful words.