Category:Hydrogen

This category concerns the topic: terms related to hydrogen.

This category contains no dictionary entries, only other categories. The subcategories are of two sorts:

• Subcategories named like "aa:Hydrogen" (with a prefixed language code) are categories of terms in specific languages. You may be interested especially in Category:en:Hydrogen, for English terms.
• Subcategories of this one named without the prefixed language code are further categories just like this one, but devoted to finer topics.

NOTE: This is a "related-to" category. It should contain terms directly related to hydrogen. Please do not include terms that merely have a tangential connection to hydrogen. Be aware that terms for types or instances of this topic often go in a separate category.