"The cat sat on mat" instead of "the cat sat on the mat" — small function words vanishing from a sentence is a different pattern from guessing whole words, with its own cause and its own fix.

Why small words disappear
Function words like the, a, of, to, is carry little visual weight and get almost no stress when spoken aloud in normal speech — the brain treats them as low-priority filler around the "important" content words. Once eyes start moving a little faster than decoding speed can strictly justify, these low-priority words are the first casualties.
Skipping is not the same as guessing
Guessing (covered in our guessing words guide) means substituting a different word. Skipping means the word is dropped entirely from the sentence. Both relate to reading habits, but the underlying cause — and the fix — is different.
The fix: finger-tracking + slowing down
- Have your child point to each word as they read it — including the small ones — for a week or two. This forces the eyes to physically land on every word.
- Slow the overall pace by one notch. A touch slower with full accuracy beats fast-with-drops every time at this stage.
- If small words are also read incorrectly (not just skipped), drill them specifically — see our tricky words list for the common function words by phase.
Word-skipping usually fades on its own as fluency builds — see our guide to what comes after phonics for how that transition works.