“Begin” is an irregular verb with three key forms: the base form begin, the past simple began, and the past participle begun. Use begin for present and infinitives, began for finished past events, and begun with auxiliary verbs to build perfect tenses and passive voice. Learning which situations need began versus begun is the main point of this set.

Use begin for the present tense with I, you, we, they, and after modals like will, can, should. It also appears in the infinitive to begin and in the -ing form beginning for progressive tenses. The base form does not show past time by itself.

Use began as the simple past form for actions that started in the past and are viewed as completed or as a past fact. It does not need an auxiliary verb and should not follow have or be. If you can replace the verb with another simple past form like went or saw, began usually fits.

Use begun as the past participle, which requires an auxiliary such as have, has, had, or be. It commonly appears in perfect tenses to connect a past start to another time reference. Begun cannot stand alone as the main verb without an auxiliary.

Use have or has with begun to form the present perfect when the start matters now, or when the exact time is not the focus. Use had with begun for the past perfect when one past start happened before another past event. The auxiliary carries the tense, and begun stays the participle.

Subject	Form	Example
I	have begun	I have begun the project.
you	have begun	You have begun to understand.
he	has begun	He has begun a new job.
she	has begun	She has begun to cook.
it	has begun	It has begun to rain.
we	have begun	We have begun the meeting.
they	have begun	They have begun work.

Use beginning with be to show an action in progress: am, is, are beginning in the present; was, were beginning in the past. This focuses on the process of starting rather than the fact that it started. Beginning is not interchangeable with began or begun because it expresses ongoing action.

Use begun with be to form the passive when the subject receives the action of starting. This is common in formal or informational writing about events, projects, or processes. The agent can be omitted if it is unknown or unimportant.

Rule	Example
Use be + begun for passive	The ceremony was begun at noon.
Use get + begun for informal passive	The project got begun late.
Keep begun with an auxiliary in passive	The work has been begun already.

Certain time expressions strongly suggest a specific form. Simple past markers like yesterday or last night usually go with began. Perfect markers like already, just, and yet often go with have begun or had begun, depending on the time frame.

Rule	Example
Finished past time often uses began	We began yesterday.
Result up to now often uses have begun	We have already begun.
Earlier past start uses had begun	They had begun before I arrived.

Begin appears in several common grammatical patterns that control what follows. Begin to + verb is frequent in careful writing, while begin + -ing is also common and sometimes feels more natural in conversation. Begin with + noun describes what you do first in a sequence.

Rule	Example
begin to + verb	She began to speak.
begin + verb-ing	She began speaking.
begin with + noun	Begin with the basics.

Begin has stress on the second syllable, which affects vowel clarity and rhythm in connected speech. The -un in begun sounds like a short vowel similar to the vowel in fun in many accents. Listening for stress helps you distinguish begin from begun in fast speech.

Rule	Description	Notation	Example
Stress pattern	Second syllable is stressed	bi GIN	Begin the lesson.
Past vowel change	Past simple changes the middle vowel sound	bi GAN	They began at six.
Participle vowel	Participle uses the -un vowel like fun	bi GUN	It has begun.