According to William Adams, the term synagogue (including the plural) occurs twenty-five times in the Book of Mormon. The first is found in a sermon by Nephi: "Behold, hath he commanded any that they should depart out of the synagogues, or out of the houses of worship? (2 Nephi 26:26)
This passage is only a few decades from the time that Lehi left Jerusalem. Hence it appears that he and his family brought the already existing concept with them to America. This passage also suggests that synagogues were used for worship in Nephi's day. This raises the question: How did Nephites worship? A number of later passages describe visitors preaching and teaching in synagogues (see Alma 16:13; 21:4,5,16; 26:29; 32:1; Moroni 7:1). Public discussions of scripture topics in the synagogues were evidently a part of that teaching and preaching (see Alma 21:5,11). Prayer apparently was also a part of the worship (see Alma 31:12-14 on Zoramite worship). This last passage also suggests that synagogue worship was held on only one day of the week and that people had the misconception that God could be worshiped only on that day and only in a synagogue (see Alma 32:2,5,9,10,12; 33:2). Other aberrant synagogue worship practices are mentioned in a sermon given by Jesus in 3 Nephi wherein he denounced public almsgiving and loud praying both in synagogues and in the streets (see 3 Nephi 13:2,5).
A related term in the Book of Mormon is church. However, the two hundred plus occurrences of church / churches in the Book of Mormon seem to point to a movement or organization rather than a building. The single exception is 4 Nephi 1:41, wherein the word churches seems to refer to structures that people could adorn.
Perhaps one can gain perspective on Book of Mormon synagogues by studying biblical synagogues. One aspect of our understanding of biblical synagogues that has been reevaluated in the light of new research is the view that synagogues did not exist until after the Babylonian captivity. Lee I. Levine, a leading scholar on the history of the synagogue, has suggested that synagogues did exist before the Babylonian captivity in the form of chambers in the city gates. Such gates have been excavated by archaeologists at such important Old Testament sites as Beersheba, Gezer, Lachish, and Megiddo. Each of these has:
1. at least one chamber (which is nearly square) lined with stone benches around the interior walls (the benched chamber at Lachish has two tiers of benches,
2. a single doorway, and
3. a niche perhaps used as storage for ritual or sacred items (where there is enough of the original wall left to determine it).
Levine concludes that since later synagogues closely mirror the architecture of the gate chambers, these chambers may well have been the original synagogues. This conclusion is supported by a number of biblical passages that indicate that the city gate and its vicinity were the hub of a community's life. The gate area served as:
1. the market place (see 2 Kings 7:1),
2. the general court (see Genesis 23:10,18; Deuteronomy 17:5, 21:19 and 22:24; Ruth 4:1-12; Jeremiah 38:7; Daniel 2:48-49; and Esther 5:9,13; 6:10,
3. the royal court (see 2 Samuel 18:4 and 19:8; and 1 Kings 22:10, which equals 2 Chronicles 18:9), and
4. a place of worship (see 2 Kings 23:8 and Nehemiah 8:1).
If Levine is correct, then, before the captivity, a town's or city's social activities centered around the city gate, and it seems reasonable that these social activities included Sabbath worship in a chamber of the gate that resembled later synagogues and functioned similarly.
Unfortunately, in the Book of Mormon the worship aspect of synagogues is mentioned only incidentally, while other functions were apparently not considered germane to the overall objective of the Small Plates or Mormon's abridgment. [William J. Adams Jr., "Synagogues in the Book of Mormon," in Journal of Book of Mormon Studies, Vol. 9, Num. 1, pp. 6-13 ] [See the commentary on Alma 16:13, 21:4-5, 31:12]