Yehoshua "bin" Nun

BaMidbar 13:8 "For the Tribe of Efrayim,  Hoshea bin Nun"

The Torah uses the unique form "bin Nun" rather than "ben Nun" to express the idea that he was the son of Nun. 

The RaMBaN explains the reason for "bin" instead of "ben" is because Yeshoshua's name is closely linked to his father, that one of Yehoshua's main qualities was his attachment to his father, and his ancestry.  And since BIN is from Binah = Understanding, it is referring to that Yehoshua was filled with wisdom and understanding. 

Hoshea was given a "pregnant soul" to fortify his resolve to be truthful and because of Hoshea's humility and the danger of peer pressure influences because of this character trait, he was given the spiritual favor of the yud before his name and permanently designated as that son of Yosef that would worthily succeed such a great man as Moshe was, by pronouncing him bin instead of ben

Not only was Hoshea "Hashem's Own" by being Yehoshua, but he was given the special Grace of Understanding from the Sefirah of Binah, or, in other words, was privileged to have a permanent connection with the Bat Kol, which he needed to worthily succeed Moshe. (AbY)

An alternate interpretation from the Sefer HaMedrash v'Hamaseh: Normally, our Rabbis tell us, there are three partners in man --his father, his mother, and G-d. In truth, however, there can be another partner in the creation of man, and that is his Rebbe, his teacher. As Chazal (our Rabbis) say, "Whoever teaches the son of his neighbor Torah, it is as if he gave birth to him." Unfortunately, this is usually not the case. The relationship between Rebbe and Talmid (student) is usually not as strong as the relationship between father and son. There are, however, cases where the Talmid is such a dedicated student (Talmid-muvhak), that the student can truly be considered the child of his Rebbe.

Yehoshua was such a Talmid. Our Rabbis describe him as the disciple par excellence, who never left the side of Moshe, his teacher. Chazal say that when Moshe finished giving a shiur (lesson), the Elders would leave. There would be some Talmidim still present and then they, too, would leave. Finally, Moshe Rabbeinu would walk and Yehoshua bin Nun would follow him. Because Yehoshua was such a dedicated Talmid, he received more from Moshe than any other individual, and eventually became Moshe's successor.

Consequently, we can actually say about Yehoshua bin Nun that he had another partner in his making. That partner was Moshe Rabbeinu. That is why, the Sefer HaMedrash v"Hamaseh says, Yehoshua was called Bin Nun, with a single dot (chirik) under the letter bet rather than the three dots (segol).  Yehoshua was the son of Nun, but not fully the son of Nun. The Torah, symbolically, took away from the full "ben" (with a segol) relationship that Yehoshua had with his father, to show that in this case his teacher had an even greater role in his development than did his father.