To Do Without
To Miss An Event, To Fail To Do
transitive verb, godan verb
Remember how 欠 mans lack? This verb is related. The 欠かす form is a little tricky, but it's sort of like you're causing yourself to lack something. So it means to do without. Depending on the context, it can also mean to miss an event or to fail to do something. Just keep in mind this word is most often used in the negative, like 欠かせないもの (things you can't do without) or 朝のコーヒーは欠かさない (never go without morning coffee).
You can remember 欠かす this way: Since you cause yourself to lack something with this word, it's all your fault. That's why you want to cuss (かす). You made yourself miss out on something. Well, $*%!!!
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You learned this reading already so you should be able to read it!
服用を欠かす
to miss a dose
食事を欠かす
to miss a meal
ランニングを欠かす
to miss a run
毎日の生活にヨガは欠かせません。
I can't miss yoga in my daily life.
このチームの仲間は一人も欠かすことができないくらい大切だ。
Each member of the team is indispensable and important.
私の生活に、携帯電話を欠かすことはできない。
I cannot live without my cell phone.