בנוגע איסור אישה לבעלה

This write up is an investigation into an identical biblical term—shichvas zera—which is interpreted by the Bavli to mean 3 different things, depending on context; and the intersection—or lack thereof—between issurei sotah and eishes ish

All issurei biah are transgressed with העראה alone. 

גמר ביאה is only required by a שפחה חרופה as the Torah says וְ֠אִ֠ישׁ כִּֽי⁠־יִשְׁכַּ֨ב אֶת⁠־אִשָּׁ֜ה שִׁכְבַת⁠־זֶ֗רַע (Vayikrah 19:20) with the Talmud explaining (kerisos 9a) למעוטי המערה. 

The איסור of אשת איש is certainly violated with העראה alone. 

When a married woman is unfaithful to her husband (or even in a case of rape if her husband is a kohen) she becomes forbidden to her husband. 

As the pasuk (Bamidbar 5:13) states by the sotah וְשָׁכַ֨ב אִ֣ישׁ אֹתָהּ֮ שִׁכְבַת⁠־זֶ֒רַע֒ that would seem to indicate that gmar biah is necessary to create an איסור אישה לבעלה, with the result being a sharp distinction between the issur eishes ish (which is violated with ha'ara'ah) vs a wife's issur vis a vis her husband (which is only generated with gmar biah).

However, there too (by the issur eishes ish) the pasuk (vayikra 18:20) says: וְאֶל⁠־אֵ֙שֶׁת֙ עֲמִֽיתְךָ֔ לֹא⁠־תִתֵּ֥ן שְׁכׇבְתְּךָ֖ לְזָ֑רַע לְטׇמְאָה⁠־בָֽהּ presumably also requiring gmar biah to transgress, which is patently not the case.

It turns out that theres an explicit gemara (tb yevamos 55b) that deals with what "shichvas zera" comes to exclude, positing 3 varying exclusions, relative to the subject matter. 

The gemara says that by shifcha charufa the language indeed excludes anything less than gmar biah, but by the other two they come to exclude other things, namely, relations with an אבר מת or posthumously by the issur eishes ish, and קינוי דרך אברים with regard to the issur sotah, with the implication being, and Rashi & Ritva writing explicitly, that העראה, however one defines it, is sufficient by them both. 

In any event, it's clear in the gemara, that practically identical language aside, theres shifcha charufa on the one hand requiring gmar biah, and the issurei sotah and eishes ish triggered/transgressed with העראה alone, like all other issurei arayos. 

From the fact that the gemara in yevamos doesn't exclude kinui with an eiver meis by the sotah (as it does with the issur eishes ish) it seems that it would be an issue (unless you say the gemara is going according to the opinion that holds eiver meis is a valid biah).

Rambam clearly holds of this distinction. 

He states (sotah 1:1) קִנּוּי הָאָמוּר בַּתּוֹרָה (במדבר ה':י"ד) וְקִנֵּא אֶת אִשְׁתּוֹ הוּא שֶׁיֹּאמַר לָהּ בִּפְנֵי עֵדִים אַל תִּסָּתְרִי עִם אִישׁ פְּלוֹנִי. אֲפִלּוּ הָיָה אָבִיהָ אוֹ אָחִיהָ אוֹ עַכּוּ"ם אוֹ עֶבֶד אוֹ שָׁחוּף הוּא הָאִישׁ שֶׁאֵינוֹ מִתְקַשֶּׁה וְאֵינוֹ מוֹלִיד explicitly saying that kinui (and presumably the issur that would follow from this particular warning) is effective by a shachuf, which he defines as a man incapable of קישוי.

However, he is on the books as holding that tashmish with an eiver meis isnt an issue vis a vis all issurei biah (issurei biah 1:11): כָּל הַבָּא בִּיאָה אֲסוּרָה בְּלֹא קִשּׁוּי. אֶלָּא שֶׁהָיָה הָאֵיבָר שֶׁלּוֹ מְדֻלְדָּל כְּמוֹ אֵיבָר הַמֵּתִים כְּגוֹן הַחוֹלִים. אוֹ מִי שֶׁנּוֹלַד כָּךְ כְּגוֹן סְרִיס חַמָּה אַף עַל פִּי שֶׁהִכְנִיס אֶת הָאֵיבָר בְּיָדוֹ אֵינוֹ חַיָּב לֹא כָּרֵת וְלֹא מַלִקוֹת וִאֵין צָרִיךְ לוֹמַר מִיתָה. שֵׁאֵין זוֹ בִּיאָה. אֲבָל פּוֹסֵל הוּא מִן הַתִּרוּמָה. וּבֵית דִּין מַכִּין אֵת שִׁנֵיהֵם מַכַּת מַרִדּוּת. 

Apparently Rambam is of the opinion, following the gemaras implication, that although one doesnt transgress the issur eishes ish with an eiver meis yet still and all it would generate an issur sotah l'ba'alah.

See Shu"t Beis Halevi 2:40:5 that fleshes this out, showing that Rambam (with Tur and SA following suit) holds that the issur isha lbaalah can even be generated by relations with an eiver meis provided that it was preceded by kinui. 

Apparently the Bavli is of the opinion, uniformity of phraseology notwithstanding, that the 3 pesukim operate on different playing fields, with 3 disparate sets of halacha controlling, depending on the given topic they are each uniquely associated with.