n. 1
The act of doing that which begins anything; commencement of an action, state, or space of time; entrance into being or upon a course; the first act, effort, or state of a succession of acts or states.
n. 2
That which is begun; a rudiment or element.
n. 3
That which begins or originates something; the source or first cause.
What was the beginning of the dispute?
adj. 1
Being the first portion of some extended thing.
in the beginning section of the course

Forms

Choose the right word

Beginning, Commencement, Commence or Begin?

The Latin commencement is more formal than the Saxon beginning, as the verb commence, is more formal than begin.

J. C. Fernald, English Synonyms and Antonyms (1914)

start As soon as it gets dark, the fireworks will start.
commencement Commencement is typically the first or second Saturday in April.
outset Tom and Mary disliked each other from the outset.
spark The science is there, what's missing is the spark.
dawning Day is dawning, and it'll soon be time to get up.

Use in printed books, per decade from 1850 to 2019.

4 letters: head¹, rise¹, root¹, dawn¹
5 letters: first¹, start¹, birth¹, prime¹, spark¹, onset²
6 letters: source¹, spring¹, origin³, outset², embryo³
7 letters: morning², opening³, initial³, element³, genesis³, infancy³, nascent², dawning²
8 letters: starting², entrance², inchoate³, rudiment³, nascency
9 letters: primitive³, inception³, incipient⁴
10 letters: foundation³, initiative⁴, initiation⁵, incipiency
12 letters: inauguration⁵, commencement³

The small number after each word is its number of syllables (onset² = 2 syllables).