Children’s expressive vocabulary and knowledge of basic concepts grow rapidly from their first words at 12 months, through first grade. Vocabulary and concepts continue to increase throughout a person’s life due to education, reading, and life experiences. Sources AutismInfo (; the Child Development Institute (

1:0 – 2:0 years 

  • Knows and uses between 200 – 300 words
  • Follows simple spatial directions, such as In and On
  • Understands Another
  • Uses simple directional terms, such as Up and Down
  • Uses two or three prepositional terms, such as On, In, or Under

2:0 – 3:0 years

  • Knows and uses up to 3,000 words
  • Distinguishes between In and Under; One and Many
  • Understands number concepts of One and Two
  • Understands size differences, such as Big and Little
  • Understands In, Off, On, Under, Out of, Together, Away from
  • Begins to understand time concepts of Soon, Later, Wait
  • Selects three that are the same from a set of four objects
  • Selects the object that is not the same from four objects with three of them identical 
  • Begins to use adjectives for color and size

3:0 – 4:0 years

  • Knows and uses up to 1,600 words
  • Follows quantity directions Empty and A lot 
  • Follows equality directions Same and Both
  • Understands Next to, Beside and Between
  • Identifies colors
  • Matches one-to-one
  • Points to an object that is different from others
  • Uses position concepts Behind, In front and Around

4 – 5 years 

  • Understands and uses 2,200 – 2,500 words
  • Understands time concepts Yesterday, Today, Tomorrow, First, Then, Next, Days of the week
  • Understands Different, Nearest, Through, Thin and Whole
  • Identifies positional concepts First, Middle and Last

5:06:0 years

  • Understands and uses 2,600 – 7,000 words
  • Understands opposite concepts, such as Big/Little, Over/Under
  • Understands Left and Right
  • Understands number concepts up to 20
  • Answers “How are things the Same and Different
  • Uses comparative adjectives, such as Loud and Louder
  • Uses Yesterday and Tomorrow
  • Uses adverbs concepts Backward and Forward
  • Uses prepositions Through, Nearest, Corner and Middle
  • Names ordinal numbers such as First, Second and Third