What principle is illustrated by the words watched, wanted, and warned?

The principle illustrated by the words "watched," "wanted," and "warned" is that the spelling of a suffix is often more reliable than its pronunciation. In these examples, the base verbs (watch, want, warn) all take the same past tense suffix “-ed” to indicate the past tense. However, the pronunciation of the suffix changes depending on the final sound of the base word.

For "watched," the "ed" is pronounced as /t/ because it follows a voiceless consonant. In "wanted," it is pronounced as /ɪd/ since it follows a voiced consonant that is not a vowel. Meanwhile, in "warned," the "ed" takes on a /d/ sound due to the final sound of "warn." This variability in pronunciation exemplifies how the spelling remains constant while the pronunciation depends on the phonetic environment, thus reinforcing that the spelling of a suffix can be more reliable than its pronunciation.

This understanding helps educators teach phonetic variations and contribute to students' awareness of how suffixes function in relation to their base words.