This is the 4th most frequent Chinese word.
一
"One"
一 (yī) is used here as a numeral to specify quantity.
我想喝一杯咖啡。
I want to drink a cup of coffee.
一 (yī) describes an unspecified small amount, showing approximation or a general sense.
在学习中,一点压力是正常的。
In studies, a little pressure is normal.
一 (yī) expresses the 'step' as part of an idiomatic phrase for gradual progress.