tap, tape, taper

[ex]
The tape seems never taper off after winding it on the tap for tens of rounds.


//=== tap
 n. 水龍頭 (tap water 就是 自來水)
 v. 輕拍,輕碰 (輕壓平板電腦的螢幕 to tap the screen of the tablet)

Tap, Double Tap, and Press and Hold on a tablet to turn it off.



//=== tape 
n. 膠帶, 錄音帶, 
casette tape recorder 卡帶錄音機

//=== taper
taper 的起源是指 蠟燭 (wax candle) , 蠟燭燃燒漸漸失去光亮 到最後完全變暗;
taper 後來就用來指 逐步消減, 常與副詞 off 連在一起用.

生命的過程大致與蠟燭類似吧, 
It seemed all of a sudden to the public that 
the famous doctor and toxicologist died a few days ago. 
In fact, he got chronical kidney disease and 
kept fighting for decades but finally tapered off. 
However, he did light and enlighten many others' life. 

逐步戒除抗焦慮/抗憂鬱藥物
 to taper off anti-anxiety and anti-depressant drugs

颱風正逐步遠離
 The storm is beginning to taper off. 

"平均來講" 質數間的間隔是越來越大 或者說越來越稀疏 (taper off)
... mathematicians have understood how the primes taper off "on average": Among large numbers, the "expected gap" between prime numbers is approximately 2.3 times the number of digits; so, for example, among 100-digit numbers, the expected gap between primes is about 230 ... 



[ref]
http://dictionary.reference.com/browse/taper 
http://dictionary.reference.com/browse/tap
https://www.simonsfoundation.org/features/science-news/unheralded-mathematician-bridges-the-prime-gap/