Third person -s
- The changes with the verb be are rather complicated. The present tense indicative third person singular form is "is" ("he is", "she is" "it is" "one is"), containing this suffix. Most other forms are "are" (second person singular and plural "you are", first person plural "we are", third person plural "they are"). In the indicative past tense, this suffix alters "was" to "were" but only for the first person singular ("I was") and third person singular ("he was", "she was", "it was", "one was").
- The verb have has a small pronunciation and spelling change - when third person -s is added, /v/ or -ve- is removed, so we say "it has" not *"it haves".
- This does not apply in the subjunctive mood, where the uninflected base form is used instead.
Third person -s is pronounced in three different ways depending on the final sound of the verb. The three pronunciations are /s/, /z/ and /ɪz/. The form is generally identical to that of plural -s and possessive 's:
The final sound of the base word determines the pronunciation of third person -s:
- /s/ for non-sibilant voiceless consonants /f/, /k/, /p/, /t/, and /θ/.
- /z/ for vowels and non-sibilant voiced consonants /b/, /d/, /ð/, /g/, /l/, /m/, /n/, /ŋ/, /r/, and /v/.
- /ɪz/ for sibilants: /s/, /z/, /tʃ/, /dʒ/, /ʃ/ and /ʒ/.
Although present in standard English, it is not found in some non-standard varieties.
Although it is a relatively straightforward rule, there is often significant delay between students first encountering it and their being able to reliably produce it. There is scope for error correction to be applied. There is a danger that it becomes a fossilised error.