Feminine versus Masculine
How can you tell the difference between a hebrew word that is feminine vs a hebrew word that is masculine?
If a word ends with ה/ת it's possible to assume it's feminine. It doesn't always work of course, but if you have to guess, you could use this "rule of thumb". The only way you can be sure is to look it up in a dictionary... Another "trick" you could use: if it's a word that has both feminine and masculine forms, then the longer form is most likely the feminine one (and again, it will probably end with either ה or ת). One important exception to this are numbers, whose longer form is actually masculine.
well, if a word ends in ת or in ה it's usually feminine. For יפה you need nikkud to know whether its feminine or masculine. keep in mind that masculine numbers are the ones with ה in the end like ארבעה אגסים, and feminine numbers don't end with ה- for example, שלוש קופסאות.