Some common synonyms for "however" are:

• Nevertheless
• Nonetheless
• Yet
• Though
• Although
• Notwithstanding
• Still
• Even so
• In spite of that
• Despite that
• Be that as it may
• Albeit
• On the other hand
• But

These synonyms can be used to express contrast or opposition between two statements or ideas. Some synonyms fit better grammatically depending on how "however" is used in a sentence—such as conjunctive adverb or adverb of manner. For example:

• "She travels by airplane frequently for work; however, she’s a nervous flier." can also be: "She travels by airplane frequently for work; nevertheless, she’s a nervous flier."
• "This diamond only weighs 0.3 carats. Its clarity, however, is amazing." can also be: "This diamond only weighs 0.3 carats. Its clarity, though, is amazing."

Other synonyms for when "however" means "in whatever way" include:

• Any way
• Whichever way
• No matter how
• In any manner
• Regardless of how

These are used more for indicating condition or manner rather than contrast. So depending on the exact meaning and grammatical usage, some best synonyms for "however" are "nevertheless," "nonetheless," "yet," "though," "although," "notwithstanding," "still," "even so," and "on the other hand".