1.
small amount; small-scale; small-lot (especially of transactions)
Used in business and finance to describe small-sized transactions, accounts, or cash. The standard pair is 小口 ('small-lot') vs. 大口 ('large-lot'), applied to orders, customers, deposits, donations, and cash handling.
小口の取引が増えた。
Small-lot transactions have increased.
経費精算には小口現金を使ってください。
Please use the petty cash for expense reimbursements.
この銀行は大口顧客だけでなく、小口の預金者にも手厚いサービスを提供している。
This bank provides generous service not only to large-scale customers but also to small-scale depositors.
2.
cut end (of a log, board, or bundle); the surface where something has been cut
The flat surface exposed when a log, piece of lumber, vegetable, bundle of paper, or similar object is cut. In cooking, 小口切り means cutting a long item (green onions, cucumbers, etc.) crosswise into thin rounds.
ねぎを小口切りにする。
Cut the green onions into thin rounds.
丸太の小口に年輪がはっきりと見えた。
The annual rings were clearly visible on the cut end of the log.
材木屋のおじさんは木材の小口に印をつけてから一本ずつ丁寧にトラックへ積み込んだ。
The lumberyard owner put marks on the cut ends of the timber and then carefully loaded each piece onto the truck one by one.
3.
edge (of a book); the three non-spine edges of a bound book
In bookbinding, the three edges of a book other than the spine — top, bottom, and fore-edge. The fore-edge is sometimes specifically called the 前小口.
本の小口が日焼けしている。
The edges of the book are sun-bleached.
古本の小口に前の持ち主のメモが書かれていた。
Notes from the previous owner were written on the edge of the secondhand book.
限定版のこの本は、小口に金箔が施されていて、棚に並べると豪華に見える。
This limited edition book has gold leaf applied to its edges, and it looks luxurious when shelved.
Compound of 小 ('small') and 口 ('mouth; opening; end'), with sequential voicing turning くち into ぐち. The sense development goes from the concrete 'small opening/end (of a cut object)' (sense 2) to the figurative business sense (sense 1). Sense 3 is a bookbinding specialization of sense 2.
USAGE:
- Sense 1 is the most frequent in modern text, especially in finance and business: 小口現金 ('petty cash'), 小口融資 ('small loan'), 小口預金 ('small-lot deposit').
- The paired contrast with 大口 is very productive: 大口注文 / 小口注文 ('large/small order').
- Sense 2 survives prominently in the cooking term 小口切り, one of the basic cutting methods taught in every Japanese cookbook.
- Sense 3 is specialist vocabulary used by publishers, bookbinders, and book lovers.
COMMON COLLOCATIONS:
- 小口現金: petty cash
- 小口取引: small-lot transaction
- 小口融資: small loan
- 小口顧客: small-scale customer
- 小口切り: thin round-slice cutting (cooking)
- 本の小口: edge of a book
SIMILAR WORDS:
- 大口: large-lot; large-scale — the direct antonym for sense 1.
- 少額: small amount (of money) — near-synonym for sense 1 when referring specifically to money, but without the 'lot size' nuance.
- 断面: cross section; cut surface — near-synonym for sense 2, more technical and general.
- 小銭: small change; coins — refers to small-denomination money; distinct from 小口 which is about transaction size, not denomination.