Sati is often found translated as mindfulness or recollection.
It is the seventh step on the noble eightfold way, the path heading to the cessation of suffering. Mindfulness, awareness, would be sampajañña (SN47,2, SN47.35) so we can quickly skip that as a valid interpretation. Of sati it is said that it means memory. It would be handy if a translation could be done by meaning and by letter, but memory doesn't quite fit hence the use of recollection. But let's look into this a bit more. First textual, by looking at what is called sati (SN45.8) and then practical, discoverable, by looking at the noble eightfold way as here the steps lead on from one to another.
As to what is called recollection:
'Here, almsmen, an almsman looking into body dwells in body as the ardent aware recollector would remove the avarice and distress about the world; ... feelings ... mind ... principles ...
This is called, almsmen, right recollection.'
And as recollection on the noble eightfold way:
'With right view, right attitude; with right attitude, right speech; with right speech, right doing; with right doing, right way of life; with right way of life, right exertion; with right exertion, right recollection; with right recollection, right concentration'.
These eight steps fall under three masses, not the other ways around, viz: the mass of behaviour, the mass of concentration and the mass of wisdom; it is thus not about the ordening of the steps on the way, but for this occasion I want to address the mass of concentration last:
Recollection would take some justification to make it seem to work; that what is called sati doesn't quite look like what we would expect to see for what recollection is at all, and it doesn't flow quite smoothly from the previous steps into the following one either. So it doesn't work. Then let's approach sati differently:
What we know is that right exertion enables right sati, and right sati enables right concentration. The four radiances (jhanā) are the summit of right concentration and from the second one on thoughts and thinking (vitakkavicāra) are not present any more. And that means that in sati they are. Right exertion creates desire, exerts and applies vigour, strains and confronts the mind for the (non)-arising of (un)arisen (un)wholesome principles. So when right exertion is exerted what is then here left to do? We can't say 'to stop thoughts and thinking' because that stilling belongs to the step ahead, so what is left?
Normally we dwell in the world, going after all sorts of interesting experiences. We can dwell in a book, we can dwell in the past, but when not falling for that, then what is there left to dwell in? Body, if what is looked into is body, or feelings if what looked into are feelings, mind ... principles ... thus to dwell in one's own domain is here what is left to do. Suppose someone is reading a book, quite absorbed, oblivious to the world outside. It can happened that when a person calls them they would not hear it. It doesn't mean they don't hear sounds; suppose there was music playing and that gets stopped, this might get noticed even though they where oblivious to what was playing; it just all became background noise. So this person is absorbed while they are seen turning the pages, while the story is very much alive for them. We call this being absorbed, dwelling, living, in the story. But how would you call it when someone sets aside the avarice and distress about the world in order to turn inwards?
I would call this meditating. So why not just call it that then? Let's see if it would fit the two points:
As to what is called meditation:
'Here, almsmen, an almsman looking into body dwells in body as the ardent aware meditator would remove the avarice and distress about the world; ... feelings ... mind ... principles ...
This is called, almsmen, right meditation.'
So far this fits nicely;
And as meditation on the noble eightfold way:
'with right exertion, right meditation; with right meditation, right concentration.'
Here too it flows smoothly right? Meditation fits within the mass of Concentration. That it sides with concentration is something even people who don't know anything about the noble eightfold way might say, let alone the wise in the world.
It doesn't seem to be the case that sati, in this context, must mean memory. It is not used that way, not in the translations nor in the Pāḷi. By looking at what it is that is called sati, and it's place on the path, we got a fitting rendering which may or may not be done by the letter, for all I know it could be a homonym. I used to find meditation vague 'what is it you do?' but explained as dwelling in body, feeling, mind, principles, so to turn inwards into one's own domain, and by telling what is preliminary done through right exertion 'by removing the avarice and distress about the world' it became quite practical.
Sati (f.) meditation.