英借文辞典 「ひ」⇒「品質保証 warranty, quality assurance
             「ほ」⇒「保証」「保証する」
         「L⇒「limited warranty
            Q⇒「quality assurance

         「W⇒「warranty」「warrant

「保証」という日本語を英訳するとき、3つの英単語が出てきます。 
                     
guarantee warranty assurance

品質はquality、保証はguarantee、だから品質保証は quality guarantee と訳す人がいます。
しかし、ビジネス英語では、quality guarantee という言葉はあまり使われません。
品質保証には2つの意味があります:
 1. 当社製品の品質保証期間は出荷後1年間です。
   The warranty term of our products is one year after shipment.
 2. 当社は品質保証システムを確立しています。
   We have established a quality assurance system for our products.

1の品質保証の意味は、「もし出荷後1年以内に当社製品が故障したら、無料で修理又は取り替えをする事を、ユーザーに対して保証する」ということです。品質保証期間 warranty term、保証期間内修理in-warranty repair、保証期間が切れている(過ぎている)out of warranty、などのように使います。

2の品質保証の意味は、「製品が品質基準に合致しているかを、設計・試作・製造・検査の全ての工程で確認する仕組みがあり、それを実行していることを保証する、請合う、自信をもって言う」という動詞 assure から来ています。品質保証部はQuality Assurance です。

では、ビジネス英語でguaranteeはどのような時に使うか?
「もし保証したことが出来なければ、賠償責任が生じるような保証」という意味によく使われます。
例えば、個人保証 personal guarantee、銀行や船会社に提出する保証状 letter of guarantee、銀行保証 banker’s guaranteeや、法規・規制を順守していることや第三者の知的財産権を侵害していないことを保証する、等です。

このように、ビジネスでは同じ「保証」でも、使う
状況で3つの英単語を使い分ける語感が必要です。

状況 1. warranty, warrant を機器の品質保証という意味で使う
通常 「Limited warranty 制限付き保証、限定品質保証」 という表現で使われる。Limited とは:
  (1) 保証期間が1年などと限定されていること、及び
  (2) 製品の使用者の過失、不注意、怠慢、過度な手荒い操作・使用条件、改造など、製造者の責任でない
    原因による故障や性能低下に対しては、保障期間内でも修理は有償となる。
機器の
品質保証書に書いてある表現
(1) 世界中で個人ユーザーに販売されている製品
(1-1) Gebew's One-Year Limited Warranty
Gebew Corporation ("Gebew")
warrants this hardware product against defects in materials and workmanship for a period of one (1) year from the date of original retail purchase. If you discover a defect, Gebew, at its option, repair, replace, or refund the pirchase price of this paroduct at no charge to you, provided you return it during the warranty period, with transportation charges prepaid, to the authorized Gebew dealer from whom you purchased it or to any other authorized Gebew dealer within the country of original retail purchase.

(1-2) Limited Warranty
Gebew Corporation product
is warranted to the original owner for a period of 180 days from the date of purchase against manufacturing defects. This warranty is covered by Gebew Corporation not the dealer from which it was purchased. Date proof of purchase is required for warranty repairs or replacement.
Should the unit become defective within the above warranty period, the unit should be returned, postage prepaid, to Gebew Corporation. The unit will be repaired or replaced at the option of Gebew Corporation. This warranty does not cover units which have been exposed to neglect, abuse, improper maintenance or unauthorized modification or repair.

(1-3) One-Year Limited Warranty
Your product
is warranted against any original defects in material or workmanship, under normal use, for one year from the date of purchase. This warranty does not apply to the batteries and other parts. Should your product develop any operation defects within the warranty period, do not return to the place of purchase but mail it to Gebew Corporation. Proof and date of purchase must accompany any return. We reserve the rights to replace your product with one of eaqual value and similar apperance at our option.

(2) 或る国で企業や専門家に販売されている製品
Gebew Equipment Limited Warranty
Gebew Corporation
warrants to its first retail purchaser that, except set forth below, the enclosed Gebew product will, at the time of purchase, be free from defects in design, materials and workmanship. For a period of one (1) year from the date of retail purchase, Gebew will, at its sole discretion, either replace or repair any defective or nonconforming component part of the product. This warranty is void and of no effect if the component part or the product is modified or altered, is subject to misuse, abuse, or lack of reasonable care, or repairs available under this warranty are made by persons not authorized by Gebew.
機器や部品の
供給・売買契約書に書いてある表現
(A) 製品に
 欠陥が無い
 ことを保証
(A-1) Supplier warrants that upon delivery and for a period of two years thereafter the products will be free from defects in design, materials and workmanship, provided that the products are not misused, modified or damaged.
(A-2) Supplier warrants that all the delivered ptoducts shall be of merchantable quality of good material and morkmanship and free from any defects.
(B) 製品が
 仕様書や
 品質要件に
 合致する
 ことを保証
(B-1) Supplier warrants to Buyer that the delivered products will be in conformity with all the requirements of a purchase order.
(B-2) Supplier expressly warrants that the goods are in accordance with the agreed specifications, drawings and other data sheets.
(B-3) Supplier warrants that the contract products shall conform to and satisfy the specifications, drawings and samples furnished, specified or approved by Buyer.
(C) 製品が
 法律・規制
 を順守する
 ことを保証
Supplier warrants that all the delivered products will conform to applicable safety and environmental rules or regulations in the countries where the products are to be sold or used.
(D) 製品に
 担保や抵当
 権が付いて
 いないこと
 を保証
Supplier warrants that all the products to be supplied hereunder shall be free of any lien, mortgage, pledge or encumbrance.
先取特権, 抵当権, 担保又は債務が付いていないこと
(E) 欠陥が
 見つかった
 場合、修理・
 代替・返金
(E-1) Supplier warrants to Buyer that the delivered products will be in conformity with all the requirements of a purchase order.If any defects are found in the products within one (1) year after the date of the title transfer, Supplier shall repair or replace by new products the defective products at no cost to Buyer within the mutually agreed period.
(E-2) If Products are found not to be as warranted within a period of twelve (12) months from the date of shipment, Buyer may, after prior notice and Supplier’s consent, return such products to Supplier, at Supplier's expense, for correction, replacement, or credit, as Buyer may direct.
ビジネス文書での例文 保証期間内である *If your machine was perchased within the last 3 years, it would be still under the warranty, and the parts would be replaced by the company at no cost to you..
 貴方の機械が過去3年以内に購入されておれば、それは未だ保証期間
  内なので、その部品は無償で会社が取替えることになります。
保証期間を過ぎている
状況 2. 「製品が品質基準に合致しているかを、設計・試作・製造・検査の全ての工程で確認する
       仕組みがあり、それを実行していることを保証する
という意味で使う。