4👑☸ Cattāri Ariya-saccaṃ 四聖諦
Learner, impure jhāna & samādhi
1. impure jhāna, is still called "jhāna"
2. Learner's low quality jhāna is still called jhāna
3. ⛔Wrong Jhāna is still called jhāna
4. Non-buddhist Jhāna is still called jhāna
1. impure jhāna, is still called "jhāna"
the 4 jhānas in the EBT, can be and are interrupted by impurities from time to time, as SN 40 and many suttas in AN 9 clearly explain. Especially when one is learning. It's just like any skill in life, if you don't practice, your skill erodes. But here is the important point. Even the impure jhāna, the Buddha still calls it "jhāna". . That's the reason for the existence of 4ip (iddhipada) and the suttas on samādhi mastery. They encourage you to remove all the impurities. The impure jhāna is impure, but its still jhāna.
⛔VRJ👻🥶 (Vism. Re-definition of Jhāna) and ⛔Jabrama👻🥶-jhana (Ajahn Brahm Re-definition of Jhāna, same as VRJ without abhidhamma theory) which describes a type of samādhi training system that is completely different, and their redefinition of what body and thinking means, contradicts the EBT and causes massive problems.
SN 40 (suttas 1-9) Moggallana's struggles with 8 samādhis
AN 9.41 the types of subverbal impurities that can occur while one is in 4 jhānas and 9 attainments.
AN 9.34 covers similar territory to AN 9.41, except Sāriputta is giving the talk, and this seems to be emphasizing it's a common experience for meditators to expect 4 jhānas and samādhi to have impurities can interrupt one while one is in jhāna.
SN 40.1 ... SN 40.9: Similar to AN 9.41, but the Buddha is helping Moggallāna with jhāna.
MN 1277 Devas attain rebirth in realms with impure radiance commensurate with the purity of their jhāna practice free of 5niv⛅ hindrances.
SN 21.1 Moggallāna is giving the talk to monks recounting the experience from SN 40.2 where the Buddha assisted him with impure second jhāna, also the sutta designates second jhāna with the special term 'noble silence'.
Moggallana is accused by other monks of claiming false samadhi attainment, for hearing sounds while in imperturbable samadhi.
imperturbable can mean fourth jhāna, but in that context, it must be one of the arupa samadhis.
The word the Buddha uses to defend moggallana, is that his samadhi is "impure" (parisuddha), but it's still a legitimate imperturbable samadhi, therefore he did not make a false claim.
2. Learner's low quality jhāna is still called jhāna
Jhāna means 'meditation'.
In 47 suttas of AN 1,
notice the Buddha uses the same word 'jhāna' to describe the four STED jhānas of AN 1.394-AN 1.397, as he does in all of these other activities.
These suttas are elided by most translators. I've expanded them out fully so you can see clearly the range of 'jhāna', and what 'being in jhāna' and what 'doing jhāna' means.
Like the AN 1 suttas above, these are calling many meditative activities like 4ip, 7sb, avitakka-avicara samadhi, "doing jhāna".
3. ⛔Wrong Jhāna is still called jhāna
Look at the passages where the buddha talks about wrong jhāna. Especially look at MN 108, KN Snp 4.7.
jhāna in the suttas just means 'meditation', or 'obsessive focus'. The fuel for the meditation/jhāna determines it as right or wrong jhāna.
B.Bodhi and B.thanissaro usually don't translate 'jhāna' as 'jhāna' when it's in a 'wrong' context, so you'll have to look at the pali.
So once you realize that wrong jhāna is still called 'jhāna', and the wrong jhāna of KN Snp 4.7 is the identical situation as the impure jhāna I cited previously, then it should dawn on you that it's just modern Theravada propaganda that elevates (the naming of) 'jhāna' into something more exalted than it actually is in the suttas.
4. Non-buddhist Jhāna is still called jhāna
Buddha did not invent jhāna
Another myth of jhāna that needs to be cleared up, is that the Buddha invented it. Look in KN Snp vagga 5, especially intro. Other brahmins, before meeting the Buddha, are said to be practicing jhāna. And later in that vagga, you see some of them could do arupa samadhis as well.
Conclusion
There is no momentary and access concentration in the EBT. There's just jhāna. It can be a wrong jhāna, a right jhāna, or impure jhāna, but the word the Buddha uses is 'jhāna'.