If by 6 months, your child does not yet:

• Enjoy playful actions
• Reach for objects
• Turn head when he/she hears a voice
• Recognize own name
• Babble or vocalize, especially when being talked or sung to

If by 9 months, your child does not yet:

• Engage in games by smiling or laughing
• Search for objects when moved out of sight
• Mouth objects or toys (oral exploration is very important!)
• Attend to music or song
• Respond to name being called
• Wave when cued or prompted

If by 12 months, your child does not yet: 

• Use gestures (reaching to be picked up/down, wave hi/bye, point to objects/toys when interested)
• Imitate gross motor movements
• Understand simple commands or questions
• Identify any body parts
• Say mama/dada (or variation) meaningfully
• Imitate animal sounds, words or environmental noises
• Use some words to gain attention, label toys/objects

If by 18 months, your child does not yet: 

• Request help when needed (especially when motivated)
• Use at least 15 words
• Use consonant sounds /t,d,n,h/ or imitate /p,b/
• Request “more”
• Name/label favorite toys or name some familiar family members

If by 24 months, your child does not yet: 

• Demonstrate pretend and symbolic play (e.g., pretend play with toys/use imagination and use objects to represent something else such as using a block to represent an ice cube in a cup)
• Put toys away when toldFollow novel commands or follow two step instructions
• Understand new words, especially when presented in various activities/situations 
• Use two word phrases (including adding new words) and use or imitate 3 word phrases
• Tell about something that happened
• Use at least 50 words

Between 24-36 months, your child should demonstrate ability to: 

• Identify body parts and clothing
• Recognize actions
• Understand use of objects (e.g., fork is for eating, cup is for drinking, crayon is for coloring)
• Demonstrate understanding of basic concepts (e.g., big/little, cold/hot, open/closed, wet/dry, etc.)
• Demonstrate understanding of quantity concepts (e.g., take one, give me some, etc.)
• Use words to ask questions, tell about something that happened, make requests, and answer yes/no consistently
• Use a variety of word combinations (i.e., phrases containing nouns, pronouns, adjectives, verbs)

You should also consider having your toddler evaluated if you notice he/she:

• Exhibits limited or inconsistent eye contact
• Does not turn when name is called
• Does not recognize familiar people’s names 
• Does not localize to sound (e.g., look toward street when ambulance passes with sirens, look toward location of loud sounds)
• Covers ears frequently when exposed to music, loud sounds, or seem bothered by commotion
• Asks “what?” frequently
• Does not appear to comprehend what was said
• Answers questions inappropriately quite often
• Does not yet initiate communication with peers or familiar adults (e.g., doesn’t seem to know how to interact with other kids at the park, doesn’t desire attention from familiar adults)
• Is not talking or saying very little.
• Talking mostly in vowels (e.g., "ih" or “ah” for “this” or “that”).
• Using one frequently produced sound or syllable to represent a variety of words.
• Not yet combining words into phrases or sentences.
• Not yet babbling or talking, was a “good baby” with little or no fussing, whining, crying

Consider having your school-aged child be evaluated for speech or language if he/she:

• Cannot be understood by peers and teachers
• Has consistent speech sound errors
• Receives speech or language services at school. Due to high caseloads, schools usually cannot offer individual sessions or the amount of minutes that would help the child progress more rapidly)
• Has difficulty expressing ideas clearly, or if language is vague
• Stutters 
• Demonstrates word finding errors
• Has a hard time learning new vocabulary words, using vocabulary words in the correct context, or has limited vocabulary
• Has a hard time with retelling of a story, movie, or event
• Exhibits difficulty with pronouns (e.g., “him went there”)
• Has difficulty with topic maintenance during a conversation
• Has difficulty understanding questions and following directions that are presented either verbally or are written