How can words sound different when spoken together in a sentence than when pronounced separately?

Words often sound different when spoken together in a sentence than when pronounced in isolation due to phonetic processes that prioritize ease of articulation and speech flow. These changes occur primarily through combinative or dependent processes, where the environment of a sound influences its production.1

Key mechanisms include:

• Assimilation: This occurs when a sound changes to become more similar to a neighboring sound to reduce the effort required for articulation. For example, in English, the phrase can't you may involve the assimilation of [t] + [j] into a single sound [tʃ]. In other languages, such as Korean, a syllable ending in a stop consonant followed by a nasal consonant will cause the stop to assimilate to the nasal sound.12
• Liaison: This happens when a syllable ending in a consonant is followed by one beginning with a vowel, causing the consonant to shift and fill the onset of the following syllable, effectively linking the two words.3
• Gemination: When words are joined, identical or similar sounds may be repeated back-to-back, sometimes perceived as a slight pause or a lengthened consonant, such as in the compound orange juice.4
• Stress and Obscuration: The intensity or stress given to syllables can shift within a sentence. Additionally, vowels in unaccented syllables often become obscured or reduced to a neutral vowel, which can alter the overall sound of words when they are part of a larger phrase.51