The term often used in the US, a 'sophomore' refers to a student who is in which year of study?

In the United States, a sophomore is a student in the second year of study at high school (Class-10) or college. In sports, sophomore may also refer to a professional athlete in their second season.

The 10th grade is the second year of a student's high school period (usually aged 15–16) and is referred to as sophomore year, so in a four year course the stages are freshman, sophomore, junior and senior. High-school sophomores are expected to begin preparing for the college application process, including increasing and focusing their extracurricular activities. Students at this level are also considered to be developing greater ability for abstract thinking.

The term sophomore is also used to refer to a student in the second year of college or university studies in the United States; typically a college sophomore is 19 to 20 years old. In the United States, college sophomores are advised to begin thinking of career options and to get involved in volunteering or social organizations on or near campus.