What is the correct form to use: "moderner" or "more modern"?

The correct form to use when comparing the adjective "modern" is "more modern" [1].

Here's why:

1. General Rule: The general rule for modifying one- or two-syllable adjectives is to add "er" or "est" to form their comparative or superlative forms. However, "modern" is an exception to this rule [1].

2. Native English Speaker's Perspective: According to a native English speaker, there are cases where you have a choice between using the "-er" form or the "more" form. However, in the case of "modern," using "moderner" would sound foreign [2].

3. Usage and Idiomaticity: The usage and idiomaticity of the language also play a role in determining the correct form. In the case of "modern," it is more common and idiomatic to use "more modern" as the comparative form [3].

Learn more:

1. More modern
2. more modern / moderner | WordReference Forums
3. adjectives - What's the comparative for the word "modern"? - English Language & Usage Stack Exchange