What significant language milestone occurs at 12 months?

The significant language milestone that typically occurs around 12 months of age is the use of single words. At this stage of development, infants begin to communicate more purposefully and may start to say simple words such as "mama" or "dada." This marks a progression from the earlier stages of language development, where they primarily rely on sounds and babbling. The emergence of single words is a crucial step in building their vocabulary and understanding of language, as it indicates that the child is starting to form connections between sounds and meanings. This milestone lays the foundation for more complex language skills that will develop as they grow older.