The definition of the word "pronunciation" is the way a word is spoken, a sequence of sounds:
Grammar/Phonetic Rules:
Three Pronunciation categories for plural -s or -es ending are Voiceless /s/, Sibilant /iz/, and Voiced /z/:
- Voiceless "s" : Singular base nouns and third person verbs ending with the letters/sounds: f, gh, k, p, ph, t, and th. Adding "s" for plural ending. The "s" is pronounced as a /s/ (soft shoosh low pitch sound, vocal cords don't vibrate, word flows smoothly). example: hats
- Sibilant "s" or "es": Singular base nouns and third person verbs ending with the letters: ce, ch, ge, s, se, sh, ss, x, z, or zz, . Adding "s" or "es" for plural ending. The "s" or "es" is pronounced as a /iz/ (an added whizzing-like low pitch vibration within the vocal cords when adding the extra ending syllable to the word): example: boxes
- Voiced "s" or "ies": Singular base nouns and third person verbs ending with the voiced constant sounds of the letters b, d, g, l, m, n, r, v, y, and dipthong or vowel (adding "s" or "ies" for plural ending) Note: An "ies" ending commonly replaces the y in consonant followed by y words - example: baby - babies). The "s" or "ies" is pronounced as a /z/. (a slight bee-like buzz high pitch vibration within vocal cords without adding an extra ending syllable) Example: dreams
~The plural word "fridges" is two syllables. Pronounced fri·juhz . Singular base word fridge (frij) with "ge" ending - SIBILANT - adding plural "s" ending pronounced as /iz/, adding an extra ending syllable to root word)
~The plural word "oranges" is three syllables. Pronounced aw·ruhn·juhz. Singular base word orange (aw·ruhnj) with "ge" ending - SIBILANT - adding plural "s" ending pronounced as /iz/, adding an extra ending syllable to root word)
~ The plural word "houses" is two syllables. Pronounced hau·zuhz. Singular base word house (haus or hauz) with "se" ending - SIBILANT - adding plural "s" ending pronounced as /iz/, adding extra ending syllable to root word)
~~~ The plural word "stores" is one syllable. Pronounced storz. Singular base word "store" (stor) with "voiced" constant sound "r" ending followed by a silent vowel e - VOICED, adding plural s ending with sound of s pronounced as /z/, does NOT add an extra ending syllable to root word)
Recommended References: Oxford English Dictionary, Cambridge Dictionary, and Merriam-Webster Dictionary.