The simplest kill command is C-k. If given at the beginning of a line, it kills all the text on the line1, leaving it blank. When used on a blank line, it kills the whole line including its newline.
More precisely, C-k kills from point up to the end of the line, unless it is at the end of a line. In that case it kills the newline following point, thus merging the next line into the current one. Spaces and tabs at the end of the line are ignored when deciding which case applies, so as long as point is after the last visible character in the line, you can be sure that C-k will kill the newline. To kill an entire non-blank line, go to the beginning and type C-k twice.
When C-k is given a positive argument n, it kills n lines and the newlines that follow them (text on the current line before point is not killed). With a negative argument −n, it kills n lines preceding the current line, together with the text on the current line before point. C-k with an argument of zero kills the text before point on the current line.
If the variable
kill-whole-line is non-
nil, C-k at
the very beginning of a line kills the entire line including the
following newline. This variable is normally
kill-whole-line) will kill a whole line
including its newline regardless of the position of point within the
line. Note that many character terminals will prevent you from typing
the key sequence C-S-backspace.