Some general rules
The words spoken as a kid learns to talk are derived by imitation of the sounds they hear. They do not have the same cross checks adult would have visualizing the written word (beginning to end) or years of repetition & correction.
At 2 about 1/2 the words they use should be understood by a stranger. By 3, 75% and by age 4, 90% would be understood. Pushing a young kid to be perfect not helpful.