소녀 is girl. we call 소녀 the age between a teenage and early twenty. "녀" comes from chinse the word "女". It means female, woman. but we don't use this word "녀" independently. "녀" must use with other words like Aàdèlio Astèllà 's example words and plus 하녀(a servant girl ), 수녀(a nun). "For the girls only" can translate in korean "오직 소녀들만을 위해". but i don't know when we use this speech. you know opposite word of 소녀 is 소년. means boy.

sonyeo - little girl nyeo - a word used as a suffix for 'female' , e.g. geu nyeo(그녀) - that girl or that lady Actually both of 'so' n 'nyeo' are chinese words, 'so' means 'little' or 'small' 'nyeo' means 'girl' , 'female' in chinese language n Korean as well, Hope this heleped