Translation guide
In Japanese, 'first period' as a school class period is commonly expressed with 一時間目 (ichijikanme) or 一限目 (ichigenme). The choice depends on formality and context.
first period
Referring to the first scheduled class in a school day.
Standard term for 'first period'. Used in most school contexts.
一時間目 is the full form and slightly more formal. 一限目 is a common abbreviation. In casual speech, 一限 is often used. All are widely understood.
First period is math.
Common abbreviation, especially in casual or university settings.
I was late for first period.
Even shorter, very casual. Often used among students.
I skipped first period.