Synonyms that are in the dictionary are marked in green. Synonyms that are not in the dictionary are marked in red.
Antonyms that are in the dictionary are marked in green. Antonyms that are not in the dictionary are marked in red.
Duplication also crops up when the site is available on multiple domains, subdomains and protocols.
Source: https://searchengineland.com/seo-website-design-build-search-engine-friendly-sites-422636