All that slopes and descends from the אמנון mountains - כל ששופע ויורד מטורי אמנון
According to רש"י the summit of טורי אמנון defines the northern border of א"י. The summit of טורי אמנון runs in an east-west direction while the mountain slopes in a north-south direction.
According to תוספות the summit of טורי אמנון defines the western border of א"י. The summit of טורי אמנון runs in a north south direction, while the mountain slopes in an east-west direction.
ר"י says anyplace that is facing א"י etc. is considered א"י, etc. - רבי יהודה אומר כל שכנגד ארץ ישראל כולי
There are those who are of the opinion that if a rectangle were drawn, in which the eastern border is the seashore of א"י, the western border is the אוקיינוס, and the north and south borders are the two lines drawn respectively from קפלוריא and נחל מצרים to the אוקיינוס; anything within this rectangle whether lands or islands would be considered א"י According to רבי יהודה. This תוספות will be discussing the ramifications of this view, as well as alternate views.
What is the ruling when one sells his slave to Suryoh? - המוכר עבדו לסוריא מהו
Those who asked the question concerning המוכר עבדו לסוריא cannot have maintained that המביא גט מסוריא צ"ל בפ"נ, for ר"ח ב"א clearly states that it is easier to attain the status of א"י for גיטין than for עבדים.
רש"י maintains that a כיבוש יחיד is a country that was captured by an individual, for his interests; not on behalf of כלל ישראל.
The ספרי maintains that any country that was conquered before א"י proper was conquered is considered a כיבוש יחיד. After all of א"י proper was conquered, any additional lands conquered, even by an individual, are considered א"י.