Worse yet when its herd pretends that it’s a noble stallion even though it could hardly be meaner or more broken-down

一匹の馬が狂えば千匹の馬も狂う
(Ippiki no uma ga kurueba senbiki no uma mo kuruu;
“When one horse goes mad, a thousand horses go mad”)

Definition:

Seeing a certain behavior from one person encourages the same behavior in others. It’s all too easy for a mob to blindly follow a bad example, just as one horse freaking out can stampede an entire herd. If you’re not careful, one bad apple will spoil the whole barrel.

Breakdown:

We begin four characters in with the noun 馬 (uma), horse, connected by the associative particle の (no) to number-counter compound 一匹 (ippiki), “one [animal].” In turn, the horse is marked as the subject of a clause by the particle が (ga), and the predicate is the verb 狂う (kuruu), “to become disordered,” “to go crazy.” This verb appears in perfective form and takes the conditional suffix ば (ba), “when,” which leads into the next clause.

Again we find a number-of-horses noun phrase, but this time the number is 千 (sen), “one thousand.” And this time the particle marking the horse is not が but も (mo), “also.” And this time the verb appears in conclusive form, making this saying into a complete sentence.

Notes:

This saying may be shortened by removing the first, or both, references to horses.

Despite Japan’s reputation for being focused on harmony and consensus, even to the detriment of the individual, the people who live there aren’t insensate to the dangers of blind following; cf. yojijukugo 付和雷同.

In English, counter words tend to be used for quantifying noncount nouns (e.g. a slice of bread, a cup of water) or more rarely for countable things that tend to appear en masse (e.g. a hundred head of cattle). In Japanese, they’re required almost every time you specify a number for a given plural noun, and matching the proper counter to a given noun can be one of the language’s more frustrating aspects for a learner. For example, 羽 (wa) is used to count birds… and rabbits, while 匹 is generally used for other small animals.

But these days in Japan, larger animals such as horses are generally counted with 頭 (tou), “head,” matching the English counter noted above. So why does this saying use 匹?

It turns out that 頭 is no coincidence: it was apparently borrowed directly from English and applied to large mammals starting with cows, but also including horses, lions, and even marine mammals such as whales and dolphins. Some collectors even use 頭, in a tongue-in-cheek way, to count butterflies! But 匹 is still valid, and in the case of horses it seems to be about twice as common as 頭. So there you have it.

Example sentence:

「どれだけ新聞を読んでも報道を見ても、完全には信じられない。一匹狂えば千匹狂うっていうけど、彼奴があらゆる制約からすり抜けて暴走したことによる被害はどのくらいあるのか本当に不安だ」

(“Dore dake shinbun wo yonde mo houdou wo mite mo, kanzen ni wa shinjirarenai. Ippiki kurueba senbiki kuruu tte iu kedo, aitsu ga arayuru seiyaku kara surinukete bousou shita koto ni yoru higai wa dono kurai aru no ka hontou ni fuan da.”)

[“I can’t quite believe it no matter how much news I read or watch. They say that one bad apple can spoil the bunch, but I’m seriously worried about how much damage that guy will cause rampaging around after slipping free from all constraints.”]