When did "transition" become a verb?

Lets look at it:

tran·si·tion

tran·si·tion [tran zísh’n]

n (plural tran·si·tions)

1. process of change: a process or period in which something undergoes a change and passes from one state, stage, form, or activity to another

2. music musical passage: a passage connecting two sections of a musical composition

3. music change of key: a progression from one key to another in a piece of music

4. grammar linking word or phrase: a word, phrase, or passage that links one subject or idea to another in speech or writing

5. physics chemistry change between phases: a change between phases such as solid to liquid or liquid to gas

6. architecture style between Romanesque and Gothic: a style of architecture in many buildings dating from the 12th century in western Europe, in which elements of the Romanesque and Gothic styles are combined

7. nuclear physics change in an atomic nucleus: a change in the energy level or state of an atomic nucleus in which a single quantum of electromagnetic radiation is either lost or gained

vti (past tran·si·tioned, past participle tran·si·tioned, present participle tran·si·tion·ing, 3rd person present singular tran·si·tions)

cause to change: to undergo a change of status or condition, or to cause somebody or something to undergo a change (informal) “We must transition Social Security from a pay-as-you-go fund to a true pension fund.” Speech by H. Ross Perot Asbury Park Press1996

[15th century. From the Latin stem transition- , from transire (see transit).]

It looks like it has been a verb for a long time.

Transition Verb

This Site Might Help You.

RE:

When did "transition" become a verb?

I always thought it was a noun. Yet I often hear and see it used as a verb these days!

It can be correctly used as either a noun or a verb.

Many words are like that ... which part of speech to classify the word as depends on how the word is used in the sentence.

Here are two examples of "transition" in different usages:

Please be patient while our department completes the transition to the new software system.

As our department transitions to the new software system, you may encounter some difficulties.

The verb is "transit". Always has been, always will be.