A student in their first year at school or university (a first-year pupil or freshman).
うちの妹は今年、小学校の一年生になった。
My younger sister became a first-year pupil in elementary school this year.
大学の一年生は履修登録の方法がまだ不慣れだ。
First-year university students are still inexperienced with course registration procedures.
教室には三十人の１年生が座っていた。
There were thirty first-year students seated in the classroom.
A beginner or novice; someone who has been in a role for less than a year (used figuratively to mean inexperienced).
彼は仕事ではまだ一年生だから、ミスがあっても仕方がない。
He's still a rookie at work, so it's understandable that he makes mistakes.
料理は私もまだ一年生で、簡単なレシピしか作れない。
I'm still a beginner at cooking and can only make simple recipes.
バンドに加入したばかりのドラマーはライブで緊張していたが、まだ一年生だと言われた。
The drummer who had just joined the band was nervous at the live show; they were told they're still a novice.
In botany: an annual plant that completes its life cycle within one year (an 'annual').
トマトは一般に一年生の植物として扱われることが多い。
Tomatoes are often treated as annual plants.
この花は一年生で、来年はまた種をまかないと見られない。
This flower is an annual, so you won't see it next year unless you sow seeds again.
Abbreviation used in botany for 'annual plant' (short for 一年生植物).
学名の説明欄に「一年生」とだけ書かれている植物があった。
There was a plant described simply as 'annual' in the description field of its scientific name.