This article will examine all 7 occurrences of the phrase "a Nephite" in the text in an attempt to clarify the sense of meaning that term held for the authors of the Book of Mormon.
Alma 8:20 "And the man [Amulek] saith (1981 & 2013 LDS editions read 'said') unto him [Alma2]: I am a Nephite." This was Amulek's declaration of political and religious affiliation. Amulek lived in Ammonihah which was the headquarters of the Nehorite/Amlicite apostasy. Five years prior to Alma's visit a major schism resulted in many former Nephites becoming political and religious Amlicites Alma 2:11. Amulek affirmed that he did not vote for Amlici in the ca. 87 B.C. plebiscite Alma 2:5-7.
Alma 19:18 "And they also saw Ammon - and behold, he was a Nephite." Lamanites in the court of King Lamoni could distinguish a foreigner in their midst. Ethnically and culturally a person of Nephite descent stood out when surrounded by Lamanites.
Alma 22:32 "And now it was only the distance of a day and a half's journey for a Nephite on the line between the land (the 1981 & 2013 LDS editions omit 'between the land') Bountiful and the land Desolation, from the east to the west sea;" Was a day and a half's journey for a Nephite an exceptional or heroic distance? No. It was neither inordinate nor impressive. The sense of the diminutive word "only" means something on a modest, pedestrian scale. "A Nephite" means a citizen of the Nephite polity. This verse tells us the Nephites had a standard unit of distance measure (1 day's journey) just as they had standard units for weight or volume (measure of barley) Alma 11:7 and value (shum, seon, etc.) Alma 11:9. The heading to 1 Nephi, Mosiah 23:3, Alma 8:6 and Helaman 4:7 all attest to this standard unit of distance measure in use among the Nephites.
Alma 49:25 "their king Amalickiah, who was a Nephite by birth," A person born to Nephite parents was considered a Nephite in the ethnic sense of that word even after they had renounced their Nephite citizenship, moved abroad and become politically active in their new homeland.
Alma 55:32 "if their wine would poison a Lamanite, it would also poison a Nephite." Here "a Nephite" is a broad term referring to any member of the Nephite nation or soldier in the Nephite army.
Helaman 4:7 "it being a day's journey for a Nephite on the line which they had fortified." Ca. 90 B.C. the Nephites stationed a military garrison on the Bountiful side of an east-west line separating the land Bountiful on the south from the land Desolation on the north. This line, terminating in the west sea, was 1.5 day's journey long Alma 22:32-33. The line described in Alma 22 is not the same as the line described here in Helaman 4 which was established ca. 35 B.C. Both lines ran from a point in the east to the west sea, but the Helaman 4:7 line was shorter by one-third and it was south of the longer line. How do we know this? Helaman 4:6 says the shorter line was entirely contained within the land Bountiful which along the Nephite west coast was south of the Bountiful/Desolation border. As we have seen above, "a Nephite" refers to any Nephite national whether citizen or soldier.
Helaman 5:35 "one among them who was a Nephite by birth." This Nephite dissenter was born to Nephite parents. He was an ethnic Nephite who had become a Lamanite in his political and religious affiliations and now resided among the Lamanites.
These verses present a clear and consistent picture. "A Nephite" was any member of the Nephite polity, a common man, an ordinary foot soldier. The hunt for elite Nephite equivalents of ultra marathoners, Olympic gold medalist distance runners or kayak racers who could have traversed the wide (216 kilometer) Isthmus of Tehuantepec in a day and a half (following Alma 22:32) or a day (following Helaman 4:7) is unwarranted and atextual.