Sentence:  The disadvantages in multi-<WSD>payline</WSD> machines are that the smaller payoffs are usually very small, much smaller than on one-<WSD>payline</WSD> machines, and also that the top jackpot is usually paid only if you line up the proper winning symbols in the correct sequence on the bottom, or third, <WSD>payline</WSD>. Or the fifth <WSD>payline</WSD> in case of the five-line machines, or the eighth <WSD>payline</WSD> in case of the eight-line machines, and so on — basically, if you don't play all the <WSD>paylines</WSD> you cannot win the jackpotl 
Meaning of the word marked with <WSD> tags:  A line of symbols on a slot machine (horizontal, vertical or diagonal) that can win a jackpot.