When children first start to speak in sentences, what is usually true of their speech?

"It is telegraphic" is true about their speech.

Telegraphic speech is characterized as a type of correspondence comprising of basic two-word long sentences frequently made out of a noun and a verb that cling to the grammatical standards of the culture's dialect. Around eighteen months of age little children create two-word sentences, for example, "Mom go" or "Daddy come."