what is its relationship with spoken language?
They  are independent of spoken languages and follow their own paths of development
Sign language
sign languages are independent of spoken languages and follow their own paths of development
ways in which infants learn the meanings of new words Infants must be able to hear and play with sounds in their environment, and to break up various phonetic units to discover words and their related meanings. at what age do they start speaking? At one year how do they develop their oral languages? Perception of speech, observe the mouth movements of others , discriminate sound phonologically what will be their first choice of words? "No" and "dada" when does babbling occur? It begins between five and seven months of age what is manual babbling? It is when infants babble with their hands and grow up using sign language how does this occur in deaf infants? Manual babbles are characterized by repetitive movements that are confined to a limited area in front of the body similar to the sign-phonetic space used in sign languages what is vocabulary spurt? UNANSWERABLE when did the sign language develop? Fifth Century BC
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Sign language [SEP] Relationships with spoken languages
Fingerspelling can sometimes be a source of new signs, such as initialized signs, in which the handshape represents the first letter of a spoken word with the same meaning. On the whole, though, sign languages are independent of spoken languages and follow their own paths of development. For example, British Sign Language (BSL) and American Sign Language (ASL) are quite different and mutually unintelligible, even though the hearing people of the United Kingdom and the United States share the same spoken language. The grammars of sign languages do not usually resemble those of spoken languages used in the same geographical area; in fact, in terms of syntax, ASL shares more with spoken Japanese than it does with English.