Considering the whole book is supposed to be just one guy's super long monologue about his life, it shouldn't be too surprising that how people talk is super-duper important to what we think about them. Let's read through two convos and check out how the whole characterization through dialogue works. First, here are Tevye and Lazer-Wolf the butcher:
"God Almighty, Reb Tevye," [Lazer-Wolf] said to me, "how come it's so hard to reach you? How are you?"
"How can I be?" I said. "I do and I do, and I'm still just beginning to get somewhere. As it says in the Torah, Neither Thy sting nor Thy honey—no money, no health, barely keeping life and limb together."
"You sin, Reb Tevye," he said to me. "Compared to the way you once were, may it never happen again, you are now, kayn eyn horeh, a rich man."
"What I still need to be a rich man," I said, "may we both have. But never mind, I thank God for what I do have. There is a saying in the Gemorah […]"
"You're always there with a quote from the Gemorah," he said to me. "Good for you, Reb Tevye, that you can read all that small print. But why waste time on all this learning and these quotations? Better let us talk about our business at hand." (4.11-15)
Check out how Lazer-Wolf presents himself: all business, no subtlety, no game, no patience for any flowery language or anything other than the basic facts. How do we know? Well, he's pretty quick to dismiss Tevye's self-deprecating nonsense about being poor. Lazer-Wolf just doesn't get Tevye's game at all, and is just like, "Dude, you were poor for reals before, and now you're not, so what are you talking about?"
And second, we know he and Tevye will never get along when Lazer-Wolf has no interest in "learning" and "quotations." That's practically Tevye's oxygen! And finally, look at the way Tevye can twist language and be funny, with his joke about the large amount of money it would take for him to be rich. Lazer-Wolf can't do that kind of thing at all, and displays his total lack of finesse by asking to get down to "business" when he's actually talking about marrying Tevye's daughter.
And now, let's see the flip side of this encounter—a conversation between Tevye and Perchik that shows that they will always be best buds:
"Tell me who you are."
"Who am I? I am a person."
"I see you're not a horse. I mean whose are you?"
"Whose should I be? I am God's." […]
"I mean where do you come from? Are you one of ours or maybe from Lithuania?"
"I come from Adam, the first man." […]
"Tell me, my young rascal, what do you live on?"
"I live on what I eat."
"Aha, that's good. But what," I said, "do you eat?"
"Everything," he said, "that they give me." (5.19-34)
These two are so 'N Sync they should change their names to Justin and Lance. Check out how both are loving this back and forth banter and joking around—at one point, Tevye even cracks up that Perchik's joke was "good." Unlike Lazer-Wolf, whose speech immediately showed that he was physically plodding and slow, Perchik's rapid fire delivery almost makes us see the skinny young guy that he undoubtedly is. They talk so well together that even the way the text puts together their speech patterns starts to be an echo—the grammar of the last two lines is identical, with a sentence broken up in the middle with speech attribution (the "I said"/"he said" part).
What does their dialogue reveal? That they are totes on the same wavelength—and that it will not be a big surprise that Tevye is cool with Hodl marrying this guy.
Since Tevye is the one telling the story, it's hard to know how much to trust his after the fact explanations and conclusions about his feelings. But we do get the sense that when he tells us about the actual events that happen and the actions that people take, he is giving us pretty much the real deal. And with that, we have a huge body of evidence for how to figure him out as a character.
Shmoop's conclusion? He's as human as they come—which means, he's a giant walking mass of contradictions.
For example, in family life, he's the kind of guy who is happy to leap over centuries of tradition and allow Tzeitl and Hodl to marry the men of their dreams, but he is also the kind of guy who is capable of entirely disowning Chava for doing the same when the man she chooses is not Jewish.
He's the kind of guy who is sensitive enough to his wife's more traditional feelings to concoct a whole one-man show to convince Golde that Tzeitl and Lazer-Wolf are a bad match, but he is also a guy who misogynistically says that women who talk are like hens that need to be slaughtered and who represses his emotions because "Tevye is not a woman."
So is he compassionate? Loving? Selfish? Authoritarian? Yes, yes, yes, and yes—he is all these things, and the complexity of his actions demonstrates just how well-rounded a creation this character really is—unlike any of the other characters, whose actions tend to all fall in line with the one thing that they're supposed to symbolize.
You know what's really missing from this book? Something that is super-standard in almost every other realist piece of fiction from the 19th century? Description. We have almost no idea what anything looks like, beyond a few generic words like "beautiful" or "schlimazel" which don't really give us a sense of actual physical characteristics, because Tevye just doesn't really seem to think it's all that important (chalk that up as another speech/dialogue quirk for him, eh?).
But it's not like we don't get any sense of the people Tevye encounters. It's just that, instead of relying on their externals to give us a sense of these people, Tevye tells us what everyone does for a living. And it does seem like in this book, to do it is to be it—everyone looks just like what the stereotypical person doing that profession would look like.
So, for example, Lazer-Wolf is a butcher. And indeed, the first thing out of his mouth is some butcher-talk: "an angry Lazer-Wolf came in, furious at the shochet, the ritual slaughterer. He had ruined him. He had declared an ox that was the size of an oak to be unkosher […]—may he have a stroke, may he sink into the earth!" (4.11) Oh, butchers! Of course, they are loud and angry and happy to talk about death at the drop of a hat—after all, that's what they do for a living, no?
Or, check out an even more telling example—Menachem-Mendl. When Tevye goes to find him in Yehupetz, there is almost no element of that guy's identity that works as a way of locating him. Tevye tries his name, his family's name, stories about his relatives—no one has ever heard of him.
Instead, the people say, "that's still not enough [for us to know who you are talking about]. What is his business? What does he deal in, your Menachem-Mendl?" And only after Tevye tells them that he's a stockbroker, are they able to connect the name to a person:
They began to laugh, then laughed louder and louder. "You mean the crook Menachem-Mendl? Why don't you just go across the street? There you'll find brokers running around like rabbits." (3.64-66)
And with that, we immediately know everything we need to know about the kind of person Menachem-Mendl will turn out to be (hint—the word "crook" really spells it out).