Children generally start to speak simple words at around 18 months of age. By two to three years of age, they should start using simple two-word utterances, and after three years of age they should be using simple sentences.

Those are the “rules-of-thumb” for language acquisition, and if a child falls behind in that schedule, psychologists and doctors take it as a sign the child might be intellectually retarded.

However, you can't always rely on the textbook. Here is an anecdote regarding the 18th century philosopher and statesman, Edmund Burke.

Edmund Burke's family was worried about him when he was a toddler, because he reached three years of age and still hadn't said his first word. They feared he might be mentally incapacitated.

But then, at a family gathering one Sunday, someone accidentally spilled some hot tea on young Edmund.

When everyone gathered around to see if he had been badly scalded, the child surprised them by speaking not just his first word but a whole sentence. The three year old uttered:

“Fear not, the pain will soon abate.” :rolleyes:

Having defied the rule-of-thumb as a child, it seems fitting that later in life Burke said, "It is the nature of all greatness not to be exact."