I started teaching my 6 year old daughter  “who is a boy and who is a girl”. It is a little confusing in Europe  to recognize girls & boys  because they both remain in almost the same get up. So I tell her that the boy is a guy who has short hair and wears a t-shirt with jeans. whereas a girl is somebody who has long hair and wears a long shirt. 

One day while going to school we saw a man with long hairs wearing t-shirt and then my daughter mentioned  me “mama , she is a girl” i cleared her ” no , he is  a boy as he has also beard on his face and some boys can have beard or mustaches on their face too” then we spot a girl with little hairs wearing t-shirt and my girl said “mama, that one is boy” i confirmed her “no, she is not boy she is girl as her t-shirt is like a girls t-shirt” 

After that I cleared her some more differences and looks about girls and boys. Any boy could keep lengthy hairs but he must have some hairs on his face too. On the other hand some girls also keep short hairs but they do not own hairs on their face. They both can wear t-shirts , jeans and trousers but girls wear some special colour outfits like pink, red and purple   whereas mostly boys wear blue and green colours  . And one more thing girls look light in weight mostly they are slim by body whereas boys have heavy body. They look powerful and hard.

That is how I made her comprehend the gender difference. Now she distinguishes between male and female. and figure out easily who is boy and who is girl