What is the real meaning of the Pali-word adukkhamasukham in the Mahasatipatthana-Sutta? In the Mahasatipatthana-Sutta are mentioned three kinds of sensations: pleasant sensations (dukkha vedana); unpleasant sensations (sukha vedana) and adukkhamasukha vedana.
What is the meaning of adukkhamasukha vedana? What are those sensations?
I think it's literally close to 'not suffering but not pleasure'

“And what is the pleasure-faculty? Any physical pleasure, physical comfort born of body-contact to be experienced as pleasure &amp; comfort. That is called the pleasure-faculty.
“And what is the pain-faculty? Any physical pain, physical discomfort
born of body-contact to be experienced as pain &amp; discomfort. That is
called the pain-faculty.
“And what is the happiness-faculty? Any mental pleasure, mental
comfort born of intellect-contact to be experienced as pleasure &amp;
comfort. That is called the happiness -faculty.
“And what is the distress-faculty? Any mental pain, mental discomfort
born of intellect-contact to be experienced as pain &amp; discomfort. That
is called the distress-faculty.
“And what is the equanimity-faculty? Anything, physical or mental, to
be experienced as neither comfort nor discomfort. That is called the
equanimity-faculty.
“With regard to this, the pleasure-faculty &amp; happiness-faculty are to
be seen as a feeling of pleasure. The pain-faculty &amp; distress-faculty
are to be seen as a feeling of pain. The equanimity-faculty is to be
seen as a feeling of neither pleasure nor pain. Thus, by this
exposition, the five are three; and the three, five.” https://www.dhammatalks.org/suttas/SN/SN48_38.html


&quot;'The thirty-six states to which beings are attached should be known': thus was it said. And in reference to what was it said? Six kinds of
household joy &amp; six kinds of renunciation joy; six kinds of household
distress &amp; six kinds of renunciation distress; six kinds of household
equanimity &amp; six kinds of renunciation equanimity.
&quot;And what are the six kinds of household joy? The joy that arises when
one regards as an acquisition the acquisition of forms cognizable by
the eye — agreeable, pleasing, charming, endearing, connected with
worldly baits — or when one recalls the previous acquisition of such
forms after they have passed, ceased, &amp; changed: That is called
household joy. (Similarly with sounds, smells, tastes, tactile
sensations, &amp; ideas.)
&quot;And what are the six kinds of renunciation joy? The joy that arises
when — experiencing the inconstancy of those very forms, their change,
fading, &amp; cessation — one sees with right discernment as it actually
is that all forms, past or present, are inconstant, stressful, subject
to change: That is called renunciation joy. (Similarly with sounds,
smells, tastes, tactile sensations, &amp; ideas.)
&quot;And what are the six kinds of household distress? The distress that
arises when one regards as a non-acquisition the non-acquisition of
forms cognizable by the eye — agreeable, pleasing, charming,
endearing, connected with worldly baits — or when one recalls the
previous non-acquisition of such forms after they have passed, ceased,
&amp; changed: That is called household distress. (Similarly with sounds,
smells, tastes, tactile sensations, &amp; ideas.)
&quot;And what are the six kinds of renunciation distress? The distress
coming from the longing that arises in one who is filled with longing
for the unexcelled liberations when — experiencing the inconstancy of
those very forms, their change, fading, &amp; cessation — he sees with
right discernment as it actually is that all forms, past or present,
are inconstant, stressful, subject to change and he is filled with
this longing: 'O when will I enter &amp; remain in the dimension that the
noble ones now enter &amp; remain in?' This is called renunciation
distress. (Similarly with sounds, smells, tastes, tactile sensations,
&amp; ideas.)
&quot;And what are the six kinds of household equanimity? The equanimity
that arises when a foolish, deluded person — a run-of-the-mill,
untaught person who has not conquered his limitations or the results
of action [2] &amp; who is blind to danger [3] — sees a form with the eye.
Such equanimity does not go beyond the form, which is why it is called
household equanimity. (Similarly with sounds, smells, tastes, tactile
sensations, &amp; ideas.)
&quot;And what are the six kinds of renunciation equanimity? The equanimity
that arises when — experiencing the inconstancy of those very forms,
their change, fading, &amp; cessation — one sees with right discernment as
it actually is that all forms, past or present, are inconstant,
stressful, subject to change: This equanimity goes beyond form, which
is why it is called renunciation equanimity. (Similarly with sounds,
smells, tastes, tactile sensations, &amp; ideas.)
https://www.accesstoinsight.org/tipitaka/mn/mn.137.than.html