Speech Sound Milestones by Age:

2 years old: You should be able to understand 50% of your child’s speech.
3 years old: You should be able to understand 75% of your child’s speech.
4 years old: You should be able to understand 100% of your child’s speech.

Language Milestones:

2 years old: Understands “no,” uses many new words, combines two words, and makes wants known.
3 years old: Asks questions, combines nouns and verbs, answers simple questions, and uses short sentences.
4 years old: Can tell a story, ask “when” and “how” questions, use pronouns, use plurals, use 4-5-word sentences and play make-believe.
5 years old: Can tell short stories, use adjectives, understand time (today, tomorrow), and most speech is grammatically correct.
6 years old: Follows and participates in simple conversations, answers open-ended questions, can retell a story, and identifies words that rhyme.