Thai อาจ and อาจจะ mark an open possibility: the speaker treats a proposition as possible without leaning strongly enough to present it as the expected outcome. Both can translate English may or might. The shorter อาจ is especially at home in concise and formal writing, while อาจจะ is the unmarked everyday conversational choice; neither changes the form of the following predicate.
The crucial contrast is epistemic possibility versus ability or permission. เขาอาจมา means “he may come”; it does not mean that he has the ability or permission to come. Those meanings use constructions such as มาได้.
One live possibility, not a prediction of the winner
เย็นนี้อาจมีฝนค่ะ เอาร่มไปด้วยนะคะ
yen ni at mi fon kha ao rom pai duai na kha
There may be rain this evening; please take an umbrella. (ordinary polite advice, female speaker; compact possibility statement)
รถไฟอาจจะมาช้าครับ เพราะฝนตกหนักทางเหนือ
rotfai at cha ma cha khrap phro fon tok nak thang nuea
The train may arrive late because it is raining heavily in the north. (ordinary polite possibility statement, male speaker)
The speaker keeps both a delayed and an on-time arrival live. Contrast an expectation:
รถไฟน่าจะมาช้าครับ ระบบแจ้งว่าล่าช้าสี่สิบนาที
rotfai na cha ma cha khrap rabop chaeng wa lacha si sip nathi
The train will probably arrive late; the system reports a forty-minute delay. (ordinary polite evidence-based conclusion, male speaker)
อาจจะ is weaker here because it merely admits the possibility. น่าจะ presents lateness as the supported probable outcome.
อาจ versus อาจจะ
The two forms substantially overlap. อาจจะ is common and natural in ordinary conversation. อาจ is compact and frequent in news, reports, instructions, academic prose, and careful speech, though it is not forbidden in conversation.
| Form | Typical distribution | Model |
|---|---|---|
| อาจ | neutral to formal; concise written clauses | การส่งของอาจล่าช้า |
| อาจจะ | neutral; especially ordinary speech | ของอาจจะมาช้า |
| อาจไม่ | compact “may not” | เขาอาจไม่มา |
| อาจจะไม่ | conversational “may not” | เขาอาจจะไม่มา |
การจัดส่งอาจล่าช้าในช่วงวันหยุด
kan chat song at lacha nai chuang wan yut
Delivery may be delayed during the holiday period. (formal customer notice)
พัสดุอาจจะมาถึงวันจันทร์ค่ะ
phatsadu at cha ma thueng wan chan kha
The parcel may arrive on Monday. (ordinary polite conversation, female speaker)
The register difference is a preference, not an absolute grammatical ban. A newsreader can say อาจจะ, and a speaker can say อาจ. Do not invent a difference such as “อาจ is past, อาจจะ is future.”
Productive slots and order
อาจ(จะ) occurs before the proposition it qualifies. Negation, obligation, ongoing viewpoint, and completion can occur inside that scope.
| Slot | Choices | Result | Interpretation |
|---|---|---|---|
| subject | เขา / ระบบ / zero | ระบบอาจหยุด | the system may stop |
| possibility | อาจ / อาจจะ | อาจจะเลื่อน | may be postponed |
| negation | ไม่ | อาจจะไม่เลื่อน | may not be postponed |
| necessity | ต้อง | อาจจะต้องเลื่อน | may have to be postponed |
| viewpoint | กำลัง...อยู่ / แล้ว | อาจกำลังซ่อมอยู่ / อาจเสร็จแล้ว | may be under repair / may be finished |
In อาจจะต้องเลื่อน, possibility has wider scope than necessity: perhaps postponement will be necessary. The following forms are not English infinitives, and Thai needs no to between them.
The negation-scope guide provides the larger system in which marker order changes meaning.
Negation: อาจไม่ versus ไม่อาจ
For “perhaps not,” use อาจไม่ + predicate or conversational อาจจะไม่ + predicate.
คุณนิดอาจไม่เข้าประชุมบ่ายนี้ค่ะ
khun nit at mai khao prachum bai ni kha
Khun Nit may not attend this afternoon's meeting. (neutral-polite workplace statement, female speaker)
ร้านอาจจะยังไม่เปิดครับ ลองโทรถามก่อน
ran at cha yang mai poet khrap long tho tham kon
The shop may not be open yet; try calling first. (ordinary polite suggestion, male speaker)
ไม่อาจ + predicate is different. It is a formal/literary construction meaning “cannot,” “is unable to,” or “cannot possibly,” not the ordinary epistemic negative of อาจ.
บริษัทไม่อาจเปิดเผยข้อมูลส่วนบุคคลได้
borisat mai at poetphoei khomun suan bukkhon dai
The company cannot disclose personal information. (formal institutional statement; inability/prohibition, not ‘may not’)
This order contrast is genuinely difficult because English may not itself can mean either uncertainty or lack of permission. Thai normally separates the readings: อาจจะไม่เปิดเผย “perhaps will not disclose,” เปิดเผยไม่ได้ “cannot/may not disclose,” and formal ไม่อาจเปิดเผยได้ “is unable to disclose.”
Time reference is independent
อาจ(จะ) can assess past, present, or future situations. Thai does not inflect the modal or the lexical predicate for those times.
เมื่อคืนเขาอาจกลับทางอื่นครับ เราเลยไม่เห็นรถ
muea khuen khao at klap thang uen khrap rao loei mai hen rot
He may have returned by another route last night, so we did not see the car. (ordinary polite speculation, male speaker; past reference)
ตอนนี้เธออาจจะพักอยู่ค่ะ อย่าเพิ่งโทรเลย
ton ni thoe at cha phak yu kha ya phoeng tho loei
She may be resting now; do not call just yet. (ordinary polite speculation, female speaker; present ongoing state)
เดือนหน้าเราอาจย้ายสำนักงานครับ
duean na rao at yai samnakngan khrap
We may move offices next month. (ordinary polite possibility statement, male speaker; future reference)
The modal expresses the speaker’s degree of commitment. เมื่อคืน, ตอนนี้, and เดือนหน้า locate the proposition. English then chooses may have returned, may be resting, or may move.
Interaction with aspect and event type
อาจ(จะ) has few lexical restrictions because it evaluates a whole proposition: it can scope over actions, changes, or states. Aspect inside that proposition must still be compatible with the event.
ช่างอาจกำลังตรวจสายไฟอยู่ครับ
chang at kamlang truat sai fai yu khrap
The technician may be checking the wiring. (ordinary polite speculation, male speaker; unfolding activity)
ฝ่ายกฎหมายอาจจะอนุมัติแล้วค่ะ แต่ระบบยังไม่อัปเดต
fai kotmai at cha anumat laeo kha tae rabop yang mai apdet
The legal department may already have approved it, but the system has not updated yet. (ordinary polite workplace speculation, female speaker; possible attainment)
Stable knowledge normally does not need a progressive: เขาอาจรู้คำตอบ “he may know the answer” is natural, while อาจกำลังรู้ is marked unless a special developing interpretation is constructed. The restriction comes from lexical aspect, not from อาจ.
Omission and discourse
When alternatives are already under discussion, Thai can omit the subject or repeated predicate: อาจจะค่ะ “maybe,” or อาจไม่ทันครับ “perhaps [we] will not make it in time.” In careful writing, retaining the proposition avoids ambiguity. Omitting อาจ(จะ) altogether removes the explicit possibility stance; context may still make a bare clause uncertain, but the grammar no longer labels it that way.
Ordinary-polite dialogue
พรุ่งนี้เราจัดประชุมที่ห้องเดิมได้ไหมคะ
phrung ni rao chat prachum thi hong doem dai mai kha
Can we hold tomorrow's meeting in the same room? (ordinary polite question, female speaker)
อาจจะไม่ได้ครับ ฝ่ายอาคารกำลังซ่อมแอร์อยู่
at cha mai dai khrap fai akhan kamlang som ae yu
Possibly not; the facilities team is repairing the air conditioner. (ordinary polite reply, male speaker)
ถ้างั้นเราอาจต้องย้ายไปห้องเล็กนะคะ
tha ngan rao at tong yai pai hong lek na kha
In that case, we may have to move to the small room. (ordinary polite assessment, female speaker)
ได้ครับ ผมจะเช็กตารางห้องก่อน
dai khrap phom cha chek tarang hong kon
All right. I will check the room schedule first. (ordinary polite reply, male speaker)
Common Mistakes
1. Using possibility for physical ability
❌ ตอนนี้ผมอาจยกกล่องนี้ครับ
Wrong for the intended ‘I am physically able to lift this box’; อาจ marks uncertainty about the proposition.
✅ ตอนนี้ผมยกกล่องนี้ไหวครับ
ton ni phom yok klong ni wai khrap
I can manage lifting this box now. (ordinary polite statement, male speaker; physical capacity)
2. Moving ไม่ before อาจ for ordinary “may not”
❌ วันนี้เขาไม่อาจมาค่ะ
Wrong for intended ordinary uncertainty; this order is formal and tends toward inability.
✅ วันนี้เขาอาจจะไม่มาค่ะ
wan ni khao at cha mai ma kha
He may not come today. (ordinary polite possibility statement, female speaker)
3. Treating อาจจะ as future-only
❌ เมื่อคืนเขาลืมกุญแจครับ
Wrong for the intended speculation—this states the forgetting as fact.
✅ เมื่อคืนเขาอาจจะลืมกุญแจไว้ที่ร้านครับ
muea khuen khao at cha luem kunchae wai thi ran khrap
He may have left his keys at the shop last night. (ordinary polite speculation, male speaker)
4. Adding an English-style complement word
❌ เราอาจจะเพื่อเลื่อนเที่ยวบินค่ะ
Incorrect—Thai does not mark the following predicate as an infinitive with เพื่อ.
✅ เราอาจจะเลื่อนเที่ยวบินเป็นวันอาทิตย์ค่ะ
rao at cha luean thiao bin pen wan athit kha
We may move the flight to Sunday. (ordinary polite possibility statement, female speaker)
Key Takeaways
- อาจ and อาจจะ keep a proposition open as possible; อาจ is especially compact/formal, while อาจจะ is common in conversation.
- Put ordinary negative possibility after the marker: อาจ(จะ)ไม่ + predicate.
- Formal ไม่อาจ...ได้ means “cannot,” not ordinary “may not.”
- Aspect and time remain independent: อาจกำลัง...อยู่, อาจ...แล้ว, and past/present/future adverbs all preserve the same possibility meaning.
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- น่าจะ for Evidence-Based ProbabilityB1 — Use น่าจะ for a probable conclusion supported by evidence, calculation, or a normal consequence, while controlling advice and negation readings.
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- Verb Chains under NegationB2 — Control the scope of Thai negation across aspect, modality, and multi-verb sequences by placing ไม่ and ไม่ได้ precisely.