The best replacement for sincerity is authenticity.

The best alternatives to sincerity are rated as following:
★★★★★  authenticity
★★★★  honesty
★★★  sarcasm

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Speaking about sincerity, one probably shouldn't forget about dignity.

Other search terms related to sincerity and their ratings are:
★★★★★ dignity
You have in mind a companion for sincerity and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of sincerity in all years. Click on graph for more.
sincerity
authenticity
honesty