The letter S

S says /s/ at the start of a word and /z/ surprisingly often elsewhere — including in most plurals, which children read before anyone explains it.

Letter sounds

s LETTER_S_01

Useful pattern · Medium reliability · Very common · Early · Reading

• /s/ unvoiced s: sun, sit, bus
• /z/ voiced s: is, has, dogs
• /ʃ/ sh sound: sugar, sure
• /ʒ/ the s of treasure: treasure, measure, usual

Where Wiggler teaches it: Skill 2: CVC Word Mastery · Skill 5: Glued Sounds & Spelling Basics

Child explanation

S usually says /s/. But listen to dogs and is — that is an s doing a /z/ sound. Both are normal.

The rule

S is /s/ at the beginning of a word, and after an unvoiced sound. Between two vowels and after a voiced sound it is usually /z/ — which is why dogs, is, has and was all carry a /z/ that nothing in the spelling shows.

What is really going on

Word-initial s is /s/ with near-total consistency. Elsewhere, voicing is assimilated to the preceding segment: after an unvoiced consonant /s/, after a voiced consonant or vowel /z/. This is why the plural and third-person -s suffix has two pronunciations that a child produces correctly in speech long before they can read them, and needs no rule to say aloud — only permission to accept when reading.

Position in the word

• Beginning of a word — Always /s/. For example: sun, sit, sad, stop.
• End of a word — After an unvoiced sound /s/; after a voiced sound /z/. For example: cats, cups, dogs, beds.
• Middle of a word — Between vowels, usually /z/. For example: nose, rose, music, easy.

Examples

Easy examples

sun, sit, is, has, dogs

More examples

sad, stop, bus, yes, cats, cups, beds, nose, rose, music, easy, was, his

Advanced examples

sugar, sure, treasure, measure, usual, vision

Pseudo-words

Made-up words that follow the rule. A child who reads these has the pattern rather than the vocabulary.

slim, nusk, besp

Contrast pairs

• cats versus dogs — The same suffix letter, two sounds, decided by the sound before it.
• bus versus buzz — Final /s/ versus final /z/, with different spellings.
• loose versus lose — Same letters, different voicing, different word.

Teacher note

Do not correct a child who reads dogs with a /z/ — that is the correct pronunciation. The point to make explicit is the opposite one: the letter is s in both cats and dogs, so when they write a plural they should not reach for z. This is a rule that matters more for spelling than for reading.

Related rules

• The -s and -es ending — -s / -es — Three sounds — /s/, /z/ and /ɪz/ — and the sound before the ending decides which. Children produce all three correctly in speech before anyone teaches them.
• SH — sh — The most reliable digraph in English. One sound, one spelling, no exceptions a child will meet.
• Soft C before E, I and Y — ce / ci / cy — C is /s/ before e, i and y. One of the clearest context rules in English — and it has real exceptions, so it should not be taught as absolute.
• The consonants that keep one sound — b d f h j k l m n p r t v w z — Fifteen consonants represent the same sound almost everywhere they appear. They are the reliable floor the rest of the system is built on.

• Previous in Letter sounds: The letter Y — y — The clearest case in English of position deciding sound. Y is a consonant at the start of a word and a vowel everywhere else — and which vowel depends on how many syllables the word has.
• Next in Letter sounds: The letter X — x — The only English letter that normally represents two sounds at once. X is /ks/ at the end of a word, /z/ at the start, and /gz/ when the stress falls after it.
• All reading rules

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