quotation from the first chapter:

A nation is a historically constituted, stable community of people, formed on the basis of a common language, territory, economic life, and psychological make-up manifested in a common culture.

It goes without saying that a nation, like every historical phenomenon, is subject to the law of change, has its history, its beginning and end.

It must be emphasized that none of the above characteristics taken separately is sufficient to define a nation. More than that, it is sufficient for a single one of these characteristics to be lacking and the nation ceases to be a nation.

It is possible to conceive of people possessing a common “national character” who, nevertheless, cannot be said to constitute a single nation if they are economically disunited, inhabit different territories, speak different languages, and so forth. Such, for instance, are the Russian, Galician, American, Georgian and Caucasian Highland Jews, who, in our opinion, do not constitute a single nation.

It is possible to conceive of people with a common territory and economic life who nevertheless would not constitute a single nation because they have no common language and no common “national character.” Such, for instance, are the Germans and Letts in the Baltic region.

Finally, the Norwegians and the Danes speak one language, but they do not constitute a single nation owing to the absence of the other characteristics.

It is only when all these characteristics are present together that we have a nation.

there’s also his definition of Zionism:

Zionism – A reactionary nationalist trend of the Jewish bourgeoisie, which had followers along the intellectuals and the more backward sections of the Jewish workers. The Zionists endeavoured to isolate the Jewish working-class masses from the general struggle of the proletariat.