Phonology is the branch of linguistics that studies the sound system of languages, including the way sounds are produced, perceived, and organized.

A triphthong is a sequence of three vowels in a single syllable, such as the /aɪə/ in the word 'fire'. However, phonemes are individual units of sound, and a triphthong is a combination of three phonemes.

A phoneme is the smallest unit of sound that can distinguish one word from another. For example, the words 'cat' and 'cot' are distinguished by the phonemes /k/ and /t/, respectively.

Assimilation is a phonological process in which one sound becomes more like a neighboring sound. For example, in the word 'dog', the /g/ sound is assimilated to the /n/ sound, resulting in the pronunciation [dɔŋ].

Semantics is the study of the relationship between sounds and meaning. It investigates how words and phrases convey meaning and how meaning is interpreted by listeners.

All of the options are examples of phonological rules. Phonological rules describe how sounds change in different contexts.

Prefixation is the process of adding a sound or group of sounds to the beginning of a word. For example, the prefix 'un-' can be added to the word 'happy' to form the word 'unhappy'.

Suprasegmental features are features of speech that apply to more than one segment, such as syllables or words. Tone, stress, and intonation are all suprasegmental features.

Phonology is the study of the sound patterns of a particular language. It investigates how sounds are organized and used in that language.

Aphasia, dyslexia, and stuttering are all examples of phonological disorders. Phonological disorders are characterized by difficulties with the production, perception, or organization of sounds.

Metathesis is the process of changing the order of sounds in a word. For example, the word 'bird' can be pronounced as [bɪɹd] or [bɹɪd].

Voice, place of articulation, and manner of articulation are all examples of phonological features. Phonological features are the basic building blocks of phonemes.

Elision is the process of deleting a sound from a word. For example, the word 'cannot' can be pronounced as [kænət] or [kænt].

Bilabial and velar are both places of articulation, so they cannot form a phonological contrast. Voiced vs. voiceless, labial vs. dental, and plosive vs. fricative are all phonological contrasts.

Phonetics is the study of the relationship between sounds and their physical properties. It investigates how sounds are produced, transmitted, and perceived.