now and then
  有時,不時,偶爾
  Now adv.
  1. At the present time; at this moment; at the time of speaking; instantly; as, I will write now.
     I have a patient now living, at an advanced age, who discharged blood from his lungs thirty years ago.   --Arbuthnot.
  2. Very lately; not long ago.
  They that but now, for honor and for plate,
  Made the sea blush with blood, resign their hate.   --Waller.
  3. At a time contemporaneous with something spoken of or contemplated; at a particular time referred to.
     The ship was now in the midst of the sea.   --Matt. xiv. 24.
  4. In present circumstances; things being as they are; -- hence, used as a connective particle, to introduce an inference or an explanation.
     How shall any man distinguish now betwixt a parasite and a man of honor?   --L'Estrange.
     Why should he live, now nature bankrupt is?   --Shak.
     Then cried they all again, saying, Not this man, but Barabbas.  Now, Barabbas was a robber.   --John xviii. 40.
     The other great and undoing mischief which befalls men is, by their being misrepresented.  Now, by calling evil good, a man is misrepresented to others in the way of slander.   --South.
  Now and again, now and then; occasionally.
  Now and now, again and again; repeatedly. [Obs.] --Chaucer.
  Now and then, at one time and another; indefinitely; occasionally; not often; at intervals. “A mead here, there a heath, and now and then a wood.” --Drayton.
  Now now, at this very instant; precisely now. [Obs.] “Why, even now now, at holding up of this finger, and before the turning down of this.” --J. Webster (1607).
  Now . . . now, alternately; at one time . . . at another time. “Now high, now low, now master up, now miss.” --Pope.
  Then adv.
  1. At that time (referring to a time specified, either past or future).
     And the Canaanite was then in the land.   --Gen. xii. 6.
     Now I know in part; but then shall I know even as also I am known.   --1 Cor. xiii. 12.
  2. Soon afterward, or immediately; next; afterward.
     First be reconciled to thy brother, and then come and offer thy gift.   --Matt. v. 24.
  3. At another time; later; again.
     One while the master is not aware of what is done, and then in other cases it may fall out to be own act.   --L'Estrange.
  By then. (a) By that time. (b) By the time that. [Obs.]
     But that opinion, I trust, by then this following argument hath been well read, will be left for one of the mysteries of an indulgent Antichrist.   --Milton.
  Now and then. See under Now, adv.
  Till then, until that time; until the time mentioned. --Milton.
  Note: ☞ Then is often used elliptically, like an adjective, for then existing; as, the then administration.
  now and then
       adv : now and then or here and there; "he was arrogant and
             occasionally callous"; "open areas are only
             occasionally interrupted by clumps of trees"; "they
             visit New York on occasion"; "now and again she would
             take her favorite book from the shelf and read to us";
             "as we drove along, the beautiful scenery now and then
             attracted his attention" [syn: occasionally, on
             occasion, once in a while, now and again, at
             times, from time to time]