If you call this file with the argument "?unused=true" it searches for the translation strings that exist in en_US but are never used.
IMPORTANT: that can take quite a lot of time (up to 10 minutes), you need to tune the max_execution_time on your php.ini accordingly.
Happy translating :)

Duplicate strings in lang files in ../../htdocs/langs/en_US/ - 90 found

#StringFile and lines
1LineIdaccountancy.lang (113 - Id line)
exports.lang (41 - Id of line)
2ByYearaccountancy.lang (168 - By year)
main.lang (771 - By year)
3CustomerInvoicePaymentaccountancy.lang (184 - Payment of invoice customer)
banks.lang (99 - Customer payment)
4Natureaccountancy.lang (241 - Nature)
members.lang (174 - Nature)
products.lang (161 - Nature)
5InternalUseradmin.lang (48 - Internal user)
users.lang (68 - Internal user)
6NewModuleadmin.lang (203 - New)
modulebuilder.lang (8 - New module)
7NoticePeriodadmin.lang (261 - Notice period)
holiday.lang (110 - Notice period)
8LanguageFileadmin.lang (354 - Language file)
modulebuilder.lang (49 - File for language)
9Stringadmin.lang (395 - String)
members.lang (101 - String)
10Intadmin.lang (398 - Integer)
members.lang (103 - Int)
11DateAndTimeadmin.lang (400 - Date and hour)
members.lang (104 - Date and time)
12Fieldadmin.lang (469 - Field)
blockedlog.lang (2 - Field)
exports.lang (60 - Field)
13Upgradeadmin.lang (966 - Upgrade)
install.lang (101 - Upgrade)
14Browseradmin.lang (977 - Browser)
main.lang (696 - Browser)
15Serveradmin.lang (978 - Server)
install.lang (47 - Server)
16DatabaseServeradmin.lang (980 - Database host)
install.lang (50 - Database server)
17DatabaseNameadmin.lang (981 - Database name)
install.lang (51 - Database name)
18DriverTypeadmin.lang (989 - Driver type)
install.lang (46 - Driver type)
19CompanyNameadmin.lang (1010 - Name)
companies.lang (26 - Company name)
20CreditNoteadmin.lang (1223 - Credit note)
bills.lang (283 - Credit note)
21CreditNotesadmin.lang (1224 - Credit notes)
bills.lang (284 - Credit notes)
22WithdrawalsSetupadmin.lang (1486 - Setup of module Direct debit payment orders)
withdrawals.lang (22 - Direct debit payment setup)
23Buyadmin.lang (1572 - Buy)
products.lang (48 - Purchases)
24Selladmin.lang (1573 - Sell)
products.lang (47 - Sales)
25AccountancyCodeadmin.lang (1576 - Accounting Code)
companies.lang (305 - Accounting account)
26CashDeskadmin.lang (1599 - Point of sales)
cashdesk.lang (3 - Point of sale)
27ByDefaultInListadmin.lang (1745 - Show by default on list view)
categories.lang (89 - By default in list)
28AffectedToagenda.lang (10 - Assigned to)
projects.lang (106 - Allocated to)
29Eventsagenda.lang (12 - Events)
main.lang (868 - Events)
30Locationagenda.lang (16 - Location)
stocks.lang (32 - Location)
31InterventionSentByEMailagenda.lang (79 - Intervention %s sent by EMail)
interventions.lang (38 - Intervention %s sent by EMail)
32IBANbanks.lang (32 - IBAN number)
bills.lang (424 - IBAN)
33BICbanks.lang (33 - BIC/SWIFT number)
bills.lang (425 - BIC/SWIFT)
34StandingOrdersbanks.lang (38 - Direct Debit orders)
bills.lang (230 - Direct debit orders)
35StandingOrderbanks.lang (39 - Direct debit order)
bills.lang (231 - Direct debit order)
36Accountbanks.lang (64 - Account)
compta.lang (15 - Account)
37SubscriptionPaymentbanks.lang (101 - Subscription payment)
members.lang (158 - Subscription payment)
38Paymentsbills.lang (63 - Payments)
compta.lang (83 - Payments)
39ValidatePaymentbills.lang (92 - Validate payment)
main.lang (724 - Validate payment)
40InvoiceRefbills.lang (312 - Invoice ref.)
compta.lang (208 - Invoice ref.)
41NoSupplierOrderboxes.lang (67 - No recorded supplier order)
orders.lang (78 - No purchase order)
42ShowCompanycashdesk.lang (29 - Show company)
companies.lang (321 - Show Third Party)
43DeleteFromCatcategories.lang (82 - Remove from tags/category)
compta.lang (250 - Remove from accounting group)
44Customercommercial.lang (4 - Customer)
companies.lang (268 - Customer)
45Prospectcommercial.lang (6 - Prospect)
companies.lang (266 - Prospect)
propal.lang (12 - Prospect)
46ShowTaskcommercial.lang (18 - Show task)
projects.lang (39 - Show task)
47ToPaycompta.lang (66 - To pay)
paybox.lang (14 - Do payment)
48ContractStatusClosedcontracts.lang (9 - Closed)
products.lang (75 - Closed)
49ExportsAreaexports.lang (2 - Exports)
other.lang (241 - Exports area)
50ExportableDatasexports.lang (6 - Exportable dataset)
other.lang (245 - Exportable data)
51AvailableFormatsexports.lang (27 - Available Formats)
other.lang (242 - Available formats)
52NotTheAssignedApproverholiday.lang (74 - You are not the assigned approver) (98 - You are not the assigned approver)
53CreateUserinstall.lang (57 - Create owner or grant him permission on database)
users.lang (30 - Create user)
54StatusInterInvoicedinterventions.lang (30 - Billed)
main.lang (486 - )
55Closedmain.lang (141 - Closed)
ticket.lang (65 - Closed)
56NewObjectmain.lang (209 - New %s)
modulebuilder.lang (9 - New object)
57CurrentValuemain.lang (211 - Current value) (674 - Current Value)
58Typemain.lang (213 - Type)
ticket.lang (69 - Type)
59MulticurrencyPaymentAmountmain.lang (353 - Payment amount, original currency)
multicurrency.lang (19 - Payment amount, original currency)
60Categorymain.lang (464 - Tag/category)
ticket.lang (70 - Category)
61OrderDateorders.lang (10 - Order date)
suppliers.lang (9 - Order date)
62CreatedByother.lang (104 - Created by %s)
ticket.lang (146 - Created by)
63FollowingUrlAreAvailableToMakePaymentspaybox.lang (4 - Following URLs are available to offer a page to a customer to make a payment on Dolibarr objects)
stripe.lang (5 - Following URLs are available to offer a page to a customer to make a payment on Dolibarr objects)
64PaymentFormpaybox.lang (5 - Payment form)
stripe.lang (6 - Payment form)
65WelcomeOnPaymentPagepaybox.lang (6 - Welcome to our online payment service)
stripe.lang (7 - Welcome to our online payment service)
66ThisScreenAllowsYouToPaypaybox.lang (7 - This screen allow you to make an online payment to %s.)
stripe.lang (8 - This screen allow you to make an online payment to %s.)
67ThisIsInformationOnPaymentpaybox.lang (8 - This is information on payment to do)
stripe.lang (9 - This is information on payment to do)
68ToCompletepaybox.lang (9 - To complete)
stripe.lang (10 - To complete)
69YourEMailpaybox.lang (10 - Email to receive payment confirmation)
stripe.lang (11 - Email to receive payment confirmation)
70Creditorpaybox.lang (11 - Creditor)
stripe.lang (13 - Creditor)
71PaymentCodepaybox.lang (12 - Payment code)
stripe.lang (14 - Payment code)
72Continuepaybox.lang (16 - Next)
stripe.lang (17 - Next)
73ToOfferALinkForOnlinePaymentpaybox.lang (17 - URL for %s payment)
stripe.lang (18 - URL for %s payment)
74ToOfferALinkForOnlinePaymentOnOrderpaybox.lang (18 - URL to offer a %s online payment user interface for a customer order)
stripe.lang (19 - URL to offer a %s online payment user interface for a customer order)
75ToOfferALinkForOnlinePaymentOnInvoicepaybox.lang (19 - URL to offer a %s online payment user interface for a customer invoice)
stripe.lang (20 - URL to offer a %s online payment user interface for a customer invoice)
76ToOfferALinkForOnlinePaymentOnContractLinepaybox.lang (20 - URL to offer a %s online payment user interface for a contract line)
stripe.lang (21 - URL to offer a %s online payment user interface for a contract line)
77ToOfferALinkForOnlinePaymentOnFreeAmountpaybox.lang (21 - URL to offer a %s online payment user interface for a free amount)
stripe.lang (22 - URL to offer a %s online payment user interface for a free amount)
78ToOfferALinkForOnlinePaymentOnMemberSubscriptionpaybox.lang (22 - URL to offer a %s online payment user interface for a member subscription)
stripe.lang (23 - URL to offer a %s online payment user interface for a member subscription)
79YouCanAddTagOnUrlpaybox.lang (23 - You can also add url parameter <b>&tag)
stripe.lang (24 - You can also add url parameter <b>&tag)
80AccountParameterpaybox.lang (27 - Account parameters)
stripe.lang (26 - Account parameters)
81UsageParameterpaybox.lang (28 - Usage parameters)
stripe.lang (27 - Usage parameters)
82InformationToFindParameterspaybox.lang (29 - Help to find your %s account information)
stripe.lang (28 - Help to find your %s account information)
83VendorNamepaybox.lang (31 - Name of vendor)
stripe.lang (30 - Name of vendor)
84CSSUrlForPaymentFormpaybox.lang (32 - CSS style sheet url for payment form)
stripe.lang (31 - CSS style sheet url for payment form)
85Stockproducts.lang (44 - Stock)
stocks.lang (18 - Stock)
86Stocksproducts.lang (45 - Stocks)
stocks.lang (19 - Stocks)
87Movementsproducts.lang (46 - Movements)
stocks.lang (23 - Movements)
88Suppliersproducts.lang (80 - Suppliers)
suppliers.lang (2 - Vendors)
89ListOfStockMovementsproducts.lang (87 - List of stock movements)
stocks.lang (26 - List of stock movements)
90Unitproducts.lang (163 - Unit)
stocks.lang (39 - Unit)