it is a period in animals where they become sexually active
Oestrus
If you are talking about oestrus to do with female animals (e.g. the cow in oestrus) it means that that animal is in heat. They are ready and capable to mate.
the relation between frequency and time period is ''t=1/f''
On average, the menstrual cycle (oestrus) of a female goat occurs approximately every 17 to 23 days.
The estrus cycle is regularly occurring period of sexual receptivity in most female mammals, except humans, during which ovulation occurs and copulation can take place. In some animals it happens once a year and in some twice a year. This is not the same as the menstrual cycle in humans.
Frequency = 1 / period
The period is independent of the mass.
it means that your cat is not healthy
Yes, but it is much easier for her if you wait until she is past that period. Also, you can have a cat spayed at 4 or 5 months before she goes into heat.
Oestrus is a word who's definition states among other things 'madness'.æ It is basically the period of time that some animal other than human is in heat.
ecology
about three weeks