Denser:Rarer::Loquacious:

Reticent

The word that best completes the analogy denser:rarer::loquacious: is reticent.

• Denser means having a higher concentration of something; compact.
• Rarer means having a lower concentration of something; scattered.
• Loquacious means very talkative or wordy.
• Talkative means inclined to talk a lot.
• Verbose means using more words than necessary.
• Reticent means not inclined to talk freely or openly.
• Garrulous means talkative in a rambling or tedious way.