how can languages be expressed, other than through speech?
Through sign language
Vocabulary development
The learning mechanisms involved in language acquisition are not specific to oral languages. The developmental stages in learning a sign language and an oral language are generally the same. Deaf babies who are exposed to sign language from birth will start babbling with their hands from 10 to 14 months. Just as in oral languages, manual babbling consists of a syllabic structure and is often reduplicated. The first symbolic sign is produced around the age of 1 year.
when does vocabulary develop slowly and when does it develop quickly It develops slowly around the age of one year and develop quickly around 18 months
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Vocabulary development [SEP] Development in sign languages
The learning mechanisms involved in language acquisition are not specific to oral languages. The developmental stages in learning a sign language and an oral language are generally the same. Deaf babies who are exposed to sign language from birth will start babbling with their hands from 10 to 14 months. Just as in oral languages, manual babbling consists of a syllabic structure and is often reduplicated. The first symbolic sign is produced around the age of 1 year. Young children will simplify complex adult signs, especially those with difficult handshapes. This is likely due to fine motor control not having fully developed yet.