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一寸先は闇
(Issun saki wa yami; “One sun ahead is darkness”)

Definition:

What lies before us, even an inch away, is darkness (metaphorically). The future is unknowable.

Breakdown:

We begin with a number-noun combination, but in this case the noun is a unit of measure, the sun (pronounced like “soon”), just over 30mm (or a little more than an inch). Note that the compond formed from 一 (ichi), “one,” and 寸 (sun) runs the consonants together into issun rather than ‘ichisun‘ as a beginning student of Japanese might expect. The compound modifies another noun, 先 (saki), which can act as different parts of speech and take on a variety of related meanings, but in this case means “(what lies) ahead” or “the future.” This entire noun phrase is marked by the topic particle は (wa), but all the comment we get on the topic once it has been established is another noun, 闇 (yami), “darkness.”

Notes:

Some versions of this saying add の夜 (no yo) to the end, making it “one sun ahead is a dark night.” This suggests a possible origin to the phrase in Japan before the introduction of Western gas and electric technology, when nights tended to lack public lighting and all was pitch dark unless you carried your own light.

Some people replace 一寸 with 一瞬, “an instant,” but this demetaphorization is incorrect.

This saying is included in the Kyoto iroha karuta set.

Example sentence:

ヤンキーとはちょっと違うが、一寸先は闇だから今夜か明日にでも死ぬかも知れないと言いながら学校をサボる男の子であった。

(“Yankii to wa chotto chigau ga, issun saki wa yami dakara konya ka asu ni de mo shinu kamoshirenai to iinagara gakkou wo saboru otoko no ko de atta.”)

[“He wasn’t exactly a delinquent, but he was the sort of boy who’d skip school, saying ‘Nobody knows what the future holds, so we might die tonight or tomorrow.’”]