From the comprehensive manual of abhidhamma i understandig that sanna refers to that function of the mind that can recognise qualities of an object.
For example, as very young children we live in a world in which sounds have still no meaning for us (or it must be nonverbal). The sound ‘A’ is not yet understood as the letter A, and combinations of sounds not yet as combination of letters. Sound combinations are not yet understood as meaningful words, and a combinations of sounds and moment of silence not as meaningful sentences. We all have to learn this. A great part of our early education we are all doing this.
As a understand it, sanna is that mental aspect of the mind that can distinguish (for example) different sounds because it can recognise the unique qualities of that unique sound. In this rudimentary function it is not perse about meaning yet, it refers to judicial decision aspect of the mind (i doubt if this is the right English word, in Dutch we say onderscheidingsvermogen). The ability to tell apart, the ability to discern, even when there is no meaning yet. A little child is able to hear the difference between the sound ‘A’ and the sound ‘B’ (sanna operates) but those sounds have no meaning yet before this is learned.
From the manual i understand that sanna also refers to the ability to make a sign or meaning of what is distinguished. so, after some learning at school the sound ‘A’ becomes the letter A. Now it has a meaning. The combinations of sounds ‘J’, ‘O’, ‘Y’ get a meaning. Sounds become meaningful
This is a more advanced or developed kind of sanna.
At a certain moment in time we are not even able anymore to not hear meaningful words come from someones mouth (in our own language). We are unable to hear sounds coming from someones mouth while we all started that way as children.
We even call this hearing. While there is much more going on then hearing ofcourse.
For me it is sure that ear-vinnana (for example) is just hearing. It provides the sound as it were.
Like a child who hears sounds but not yet meaningful letters and words. It is not that meaning is intrinsic to being aware, or intrinsic to ear-vinnana or whatever vinnana. Not at all. A great part of our lives we can see this. It is not that sign or meaning and awareness are the same. I feel there is also the opening to the end of suffering.
Maybe when we have become adults it looks like we live in an intrinsic meaningful world, all has meaning for us, and this meaning seems fixed, just how things are, but that is not true. Almost all meaning is learned, attributed, adventitious, result of conditioning, and not something intrinsic to what is senses, heard, seen etc
I feel the Buddha also saw that even meaning like me and mine are attributed and are not some ultimate reality.
Ofcourse suffering and the end of suffering is very closely related to what meaning something has for us.