Usually there are two semesters. Fall and Spring. The fall semester is also known as the first semester while spring semester is known as the second. The second (spring) semester begins in the winter and ends in June. No mid-term break exists in the academic calendar.
U.S Universities have two intakes for admission purposes, namely Fall and Spring semesters. Fall semester starts in late August and ends in late December or early January whereas the Spring semester begins in January and ends in early May.