I think historically, a pulpit was used for preaching, not the liturgical reading of scripture, and I believe this was the case in the eastern churches as well. The ambo is a lectern from which the scriptures are read and expounded. In larger churches, it is frequently not the pulpit. I would note also the tendency over the past few decades to incorporate Greek liturgical terms in preference to Latin derivatives, e.g. homily instead of sermon, anaphora instead of canon, even liturgy instead of service, which is already apparent in the 1960 Missal. I remember seeing an article or post about this somewhere, maybe NLM.

I would say an ambo has a liturgical function - the proclaiming of scripture - and a pulpit does not (in Catholic churches). Of course they might be the same structure, if fixed.
I gather ambo/ambones was taken into mediæval Latin from the Greek αμβον to distinguish it from pulpitum, a scaffold or other raised platform.

This is all helpful, and I thought I had it all down exactly because I was a parishioner for years at the Cathedral of St. Matthew the Apostle, where they have a pulpit (as a structure), an ambo for the proclamation of Scripture, and a lectern for announcements. Only a bishop preaches from the pulpit, and I believe that they then proclaim the Gospel from up there as well. However, memory is fuzzy, as I left that parish in 2018--no prizes for guessing what prompted that move.

But--back to ambos--I was wrong.

The National Shrine uses the pulpit for proclamation (up front, but way out of the way of the ceremony). I'm checking with someone who used to server there all the time, but I have not yet heard which one they call the ambo.

A church I used to go to in NC had just one structure, which they called an ambo. A kind of preacher's desk with little wings on the side. Modern, but dignified.

For my TLMs, St. Mary Mother of God has a pulpit for preaching, but of course proclamation is done from the altar. At another parish, during the TLM, the priest preaches from the ambo for the regular Mass, a very small lectern.

It seems, piecing it all together, that madorganist and a_f_hawkins have a good handle on it: ambo is the liturgical word and, subject to diocesan norms, it can be of almost any structure--a raised pulpit or a lectern of any shape. Live and learn. As I said, the General Instruction leaves it vague, and just says there is supposed to be one, and I realize now I have seen many architectural solutions, both modern and ancient.

The pulpit in the middle of the nave makes a lot of sense for the days when there were no microphones. I think I've only seen it once here (maybe the Shrine of St. Joseph in St. Louis), but it is common in any large church in Europe that didn't get blown up in two centuries of war.

Thanks to all.

Kenneth

My understanding is that a podium is a platform used to raise something a short distance above its surroundings and, in North American English, also means a lectern. We sometimes call the ambo a podium because it is often raised higher than the surrounding floor. A lectern is a stand or raised desk from which readings are proclaimed. Lecterns are used not only in churches but also in lecture halls and classrooms. The traditional difference (it seems) between a lectern and a pulpit is that while Scripture readings are may be proclaimed from a lectern, sermons or homilies are not. A pulpit is the proper place for a homily to be given. Often pulpits are larger or higher, more ornate, and, in older churches, may in the middle of the church building so that everyone could hear the homily before microphones were invented. They are often round or roundish with a canopy or “sounding board” above them to help with acoustics. In churches that have only one lectern from where the Scripture readings are read and also from where the homily is given call the lectern an ambo. This term comes from the Greek word ἄμβων meaning ‘crest of a hill’ or ‘pulpit.’

According to the modern rubrics, from the ambo only the readings, the Responsorial Psalm, and the Easter Proclamation (Exsultet) are to be proclaimed; likewise, it may be used for giving the homily and for announcing the intentions of the Prayer of the Faithful. The dignity of the ambo requires that only a minister of the word should stand at it.

Just in case your parish has a folding lectern - this is a legelium :
https://vanpoulles.co.uk/products/folding-legilium