fi

End if statement

$ if [ condition ]; then commands; fi

$ if [ condition ]; then commands; else other; fi

$ if [ cond1 ]; then cmd1; elif [ cond2 ]; then cmd2; fi

if condition; then commands; fi

fi is a shell keyword that closes an if conditional block. It's part of the shell's control flow syntax, marking where conditional execution ends.
The if/then/fi structure evaluates conditions and executes code blocks based on exit statuses. Conditions can use test commands, [[ ]], or any command's exit status.
fi must appear for every if, matching them like parentheses.

if

Begin conditional block.

Commands to execute if condition is true.

Else-if for additional conditions.

Commands if no conditions matched.

End of if block (if spelled backward).

Must have matching if. Requires semicolon or newline before fi. Syntax errors from missing fi are common.

fi is part of Bourne shell syntax from the 1970s. The reversed spelling of "if" matches other shell block terminators like esac (case reversed) and done (for/while/until).

if(1), test(1), bash(1)