Sentence:  'In the first month, on the fourteenth day of the month at twilight is the LORD'S <WSD>Passover</WSD>. 'Then on the fifteenth day of the same month there is the Feast of Unleavened Bread to the LORD; for seven days you shall eat unleavened bread. 
Meaning of the word marked with <WSD> tags:  The one-day Biblical feast that begins at twilight on the fourteenth day of the first month (Nisan 14), which is then immediately followed by the seven-day Feast of Unleavened Bread (Nisan 15-21).