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Some content words signal that future content will likely follow. The words seem to act as a typing system for instances of the content. For example:

"I have an idea." --> one expects the idea to soon follow

"I have an example." --> (what is the example?)

"There are two things I need to say." --> (what are the two things?)

Is there a name for these kinds of words?

User6726 is absolutely correct, but to expand a little bit:

The "more to follow" idea comes from Gricean implicature, not from the words themselves.

Grice's Maxims are four rules that people "expect" everyone in a conversation to follow. One is the maxim of relevance: if you're saying something, you're saying it for a reason, so it should be relevant to the context. Another is the maxim of quantity: you'll say as much as you need to get the point across.

"I have an idea" on its own generally seems to violate either relevance or quantity: in most contexts, that doesn't really add anything or give any useful information (bad relevance), and if the idea is relevant, you haven't said enough about it (bad quantity). But if you followed it up with "…we could foo the bar", that would fulfill both relevance and quantity. So people will be expecting that followup—it's the only way the first part makes pragmatic sense.

These words are nouns. The effect you're referring to doesn't come from those words. For example "That's why I rejected that idea", "I accepted his example", "As you know, Dr. Seuss wrote about two things". You can create an expectation of "more to come" by not saying enough.