On the whole, in spite of authorities, I am disposed to think that οἶκος is the house viewed from outside as an object set before us, οἰκία from inside; οἶκος the building as such, the temple always, so a family, or lineage metaphorically. It is very often merely a difference of conception in the writer. If I think of the house as a building to which I came, I should say, οἶκος, if I was going in to a set of people in it, or having to do with the house inside of it, not materially, but as containing, I should say, elide. We have a striking example, how near they run together, and yet have a different sense: in 1 Cor. 1:16 οἶκος of Stephanas, the family looked at objectively from without; in xvi. 15, οἰκία. The material house as from without was not the first-fruits, but the household as a whole which was so. What seems a difficulty is the end, of sermon on the Mount, building the house on a rock. (Matt. 7:24; 25 Luke 6:48, 49: as far as I find, it is always thus, ᾠκοδόμησεν οἰκίαν.) I think οἰκία is the whole concern the builder had in his mind for his habitation, a dwelling with his family, which was of course a house. Hence “go not from house to house,” is οἰκία, though they might from οἶκος to οἶκος. Cf. Matt. 5:15; Phil. 4:22, and more strongly Matt. 10:12, 13, 14; 13:51; John 4:53. In Luke 10:5, we have both. They go into the οἰκίαν or dwelling containing the family, and say, Peace be to this house, οἴκῳ, an object before their minds as one thing. They brake bread, κατ' οἶκον; and τὴν κατ' οἶκον αὐτῶν ἐκκλησίαν, meeting there, not in the household. See Acts 2:46; 5:42; 8:3; 20:20. So the blessing comes as the peace on the οἶκον, Luke 19:9. In Matt. 12:25, οἰκία κατ' ἑαυτῆς, in Luke 11:17, οἶκος ἐπὶ οἶκον. Here in Luke οἰκία would not do; it is a single whole thing, not collective as in Matthew: οἰκία would have been too intimate.