What is the earliest age at which expressive language delays can be identified?

Answer:  There is great variation in vocabulary development before 24 months.  Many children who have almost no words at 20 months are speaking well by 24 months.  A large vocabulary on the LDS from 18-23 months indicates that a child is making good progress, but a small vocabulary in that period does not necessarily indicate a significant delay.  However, by 24 months, most toddlers say at least 50 words and produce some word combinations.  A child who fails either of these milestones may therefore have a significant language delay.