MONTH, noun [Latin mensis; Gr. a month from the moon.] A space or period of time constituting a division of the year. month originally signified the time of one revolution of the moon, a lunation, or the period from one change or conjunction of the moon with the sun to another, a period of 27 days, 7 hours, 43 minutes and 5 seconds. This is the periodical month or as we generally call it, the lunar month In this sense we still use the word month But we also apply the term to the space of time in which the sun passes through one sign, or a twelfth part of the zodiac. This period contains 30 days, 10 hours, 29 minutes, 5 seconds, and it called a solar month In the year, there are twelve solar months, and thirteen lunar months.
In popular language, four weeks are called a month being nearly the length of the lunar month A calendar month differs in some degree from a solar month; consisting of twenty eight, twenty nine, thirty or thirty one days, as the months stand in calendars or almanacs.