Plain-language explanation.
Phonetics studies the physical properties of speech sounds — how they are produced, transmitted, and perceived. Phonology studies how sounds pattern within a language — which sounds contrast with each other, which sequences are allowed, and how stress and tone work.
Core concepts and standard treatment.
Articulatory phonetics classifies consonants by voicing, place of articulation (bilabial, alveolar, velar, etc.), and manner of articulation (plosive, fricative, affricate, nasal, lateral, approximant). Vowels are classified by height, backness, and rounding. The International Phonetic Alphabet (IPA) provides a universal notation system. Acoustic phonetics characterises sounds by formant frequencies, fundamental frequency (pitch), duration, and intensity.
Deeper theory, debates and edge cases.
Phonological theory: distinctive features define contrasting sound properties. Autosegmental phonology represents tone and metrical structure on separate tiers. Optimality Theory (Prince and Smolensky) reframes phonology as constraint ranking: surface forms emerge from ranking violable universal constraints. Prosody — stress, rhythm, and intonation — signals sentence structure, information structure, and pragmatic meaning. Lexical tone languages (Mandarin: 4 tones; Cantonese: 9 tones) contrast with intonation languages (English) in how pitch is phonologically structured.
How it is applied in practice.
Clinical applications: speech-language pathology treats articulation disorders, phonological disorders, dysarthria (motor speech disorder), and dysphagia. Forensic speaker comparison uses acoustic and auditory analysis to evaluate disputed identity claims. Speaker recognition technology (deep learning acoustic models) is deployed in call centres and security systems — raising concerns about bias across gender, age, accent, and language variety. Second language phonology research informs pronunciation pedagogy, addressing why certain contrasts are difficult for particular L1 speakers.