2. swirl   noun   

原句: And those doughnut-shaped swirls of water are an efficient way of propulsion.

意思: the movement of sth that twists and turns in different directions and at different speeds

字源: late Middle English (originally Scots in the sense ‘whirlpool’): perhaps of Low German or Dutch origin; compare with Dutch zwirrelen ‘to whirl’. 

例句: The dancers left the stage in a swirl of skirts.

3. identical   adjective   

原句: The systems don't need to be identical for you to learn from them.

意思: similar in every detail

字源: late 16th cent. (as a mathematical term): from medieval Latin identicus, from late Latin identitas, from Latin idem ‘same’. 

例句: The two pictures are similar, although not identical.

4. diaper   noun   

原句: I probably changed three diapers.

意思: a piece of soft cloth or other thick material that is folded around a baby's bottom and between its legs to absorb and hold its body waste

字源: Middle English: from Old French diapre, from medieval Latin diasprum, from medieval Greek diaspros (adjective), from dia ‘across’ + aspros ‘white’. The term seems originally to have denoted a costly fabric, but after the 15th cent. it was used as as a noun to denote cotton or linen woven with a pattern of small diamonds; babies' nappies were originally made from pieces of this fabric, hence the current sense (late 16th cent.). 

例句: It was time for a diaper change.

5. abiding   adjective   

原句: You never love anybody as much as you love your kid, in the deepest, most abiding way.

意思: lasting for a long time and not changing 

例句: He is an artist with an abiding concern for humanity.