Тетрадь (она/she) - feminine. Чай (он/he) - masculine. Щи (они/they) - plural, like "ножницы" (scissors). For example: Будешь щи? Они вкусные!

The noun, that ends on "и" i or "у" and is singular, can be male, female or neutral. And such nouns are always borrowed words. беби - m., гризли - m., колибри - f., гуппи - f., кенгуру - f. or m., тори - m. (political party in England), хаки (n.), сиртаки (m. or n.), макИ - m. (French partisan), буги-вуги - m. or pl. I don't think that there is a rule. You need look dictionary. But perhaps колибри and гуппи are female because птица и рыба are female.

Sorry. I'll better post them apart. http://lingvopro.abbyyonline.com/en/Search/ru-en

http://lingvopro.abbyyonline.com/en/Search/ru-en http://slovar.plib.ru/ http://slovarus.info/rus_ef.php

I'd like to give you links to very good on line dictionaries. The nouns on these dictionaries are always marked with one of the following letters: м. (мужской - masculine), ж. (женский - feminine), ср. or с. (средний - neuter), мн. (множественный - plural). http://lingvopro.abbyyonline.com/en/Search/ru-en http://slovar.plib.ru/ http://slovarus.info/rus_ef.php