1. I grew 3 cm a year.

2. I grew by 3 cm a year.

(Does #1 mean #2? Is 'by' omitted before 3 cm? Then 'grew' is an intransitive verb. If not, 'grew' is a transitive verb.)

Both are correct.

Sra

Both statements suggest that — in the past — you grew 3 cm each year. If the growth was only in one year, you could designate the year:

"I grew 3 cm last year."

I hope t his helps a little more. Thanks for asking.

In sentence #1, the phrase "grew 3 cm a year" indicates that the subject, which is not specified in your example, increased in height by 3 cm every year. Here, the verb "grew" is used intransitively, meaning it does not take a direct object.

In sentence #2, the phrase "grew by 3 cm a year" also implies that the subject increased in height by 3 cm annually. However, in this case, the verb "grew" is used transitively because it takes a direct object, which is the measurement of growth (3 cm).

Both sentences convey the same meaning, but sentence #1 omits the preposition "by" before the measurement. This omission does not change the meaning or structure of the sentence; it is simply a matter of style or personal preference.