In addition, an inability to engage in social exchanges is a sign of language delay at all ages.Communicative deficits at specific ages and milestones might indicate language delay, including:

Not smiling at 3 months
Not turning the head toward sounds at 4 months
Not laughing or responding to sounds at 6 months
Not babbling at 9 months
Not pointing and using gestures at 12 months
Not producing more than 5 words at 18 months
Not producing more than 50 words at 24 months
Losing language and/or social skills after 36 monthsLater in life, important signs include:

A lack of speech
An inability to comprehend, process, or understand language presented to the child

Consequences of Language Delay
Language delay is a risk factor for other types of developmental delay, including social, emotional, and cognitive delay. Language delay can impact behavior, reading and spelling ability, and overall IQ scores. Some children may outgrow deficits in reading and writing while others do not. Other conditions associated with language delay include attention-deficit/hyperactivity disorder, autism spectrum disorder, and social communication disorder. Causes
Language delays are the most frequent developmental delays, and can occur for many reasons. A delay can be due to being a "late bloomer", "late talker", or a more serious problem. Such delays can occur in conjunction with a lack of mirroring of facial responses, unresponsiveness or unawareness of certain noises, a lack of interest in playing with other children or toys, or no pain response to stimuli. Socio-economic factors
Socio-economic status
Children from families of low educational level are more likely to have delays and difficulties in expressive language.
For example, a child may be delayed in speech (i.e., unable to produce intelligible speech sounds), but not delayed in language because they use a Sign Language. Additionally, language delay encompasses the entirety of language developmental progress being slowed and not just the speech aspects. Language delays are recognized by comparing language development of children to recognized developmental milestones. They are presented in a variety of ways, as every individual child has a unique set of language skills and deficiencies that are identifiable through many different screenings and tools. There are different causes leading to language delay; it is often a result of another developmental disorder and treatment requires analysis of the unique individual causes. The condition is frequently observed early on, among two- and three-year-olds. Early language delays are only considered risk-factors in leading to more severe language disorders. Language Development
The anatomical language centers of the brain are the Brocas and Wernickes area. These two areas include all aspects of the development of language. The Brocas area is the motor portion of language at the left posterior inferior frontal gyrus and involves speech production. The Wernickes area is the sensory portion of language at the posterior part of the left superior temporal gyrus and involves auditory verbal comprehension.There are recognizable speech and language developmental milestones in children. For children with language delays, milestones in their language development may be different or slowed. Recent studies have shown the different milestones for children with language delay compared to children with normal language development.