diff --git a/htdocs/langs/en_US/admin.lang b/htdocs/langs/en_US/admin.lang
old mode 100644
new mode 100755
index a524ff8a5fe..3df2a8fc72d
--- a/htdocs/langs/en_US/admin.lang
+++ b/htdocs/langs/en_US/admin.lang
@@ -495,6 +495,8 @@ Module1780Name=Categories
 Module1780Desc=Category management (products, suppliers and customers)
 Module2000Name=WYSIWYG editor
 Module2000Desc=Allow to edit some text area using an advanced editor
+Module2200Name=Dinamic Prices
+Module2200Desc=Enable the usage of math expressions for prices
 Module2300Name=Cron
 Module2300Desc=Scheduled task management
 Module2400Name=Agenda
diff --git a/htdocs/langs/en_US/errors.lang b/htdocs/langs/en_US/errors.lang
old mode 100644
new mode 100755
index 0187c567eb6..35b7da13728
--- a/htdocs/langs/en_US/errors.lang
+++ b/htdocs/langs/en_US/errors.lang
@@ -138,6 +138,24 @@ ErrorMemberNotLinkedToAThirpartyLinkOrCreateFirst=Error, this member is not yet
 ErrorThereIsSomeDeliveries=Error, there is some deliveries linked to this shipment. Deletion refused.
 ErrorCantDeletePaymentReconciliated=Can't delete a payment that had generated a bank transaction that was conciliated
 ErrorCantDeletePaymentSharedWithPayedInvoice=Can't delete a payment shared by at least one invoice with status Payed
+ErrorPriceExpression1=Cannot assign to constant '%s'
+ErrorPriceExpression2=Cannot redefine built-in function '%s'
+ErrorPriceExpression3=Undefined variable '%s' in function definition
+ErrorPriceExpression4=Illegal character '%s'
+ErrorPriceExpression5=Unexpected '%s'
+ErrorPriceExpression6=Wrong number of arguments (%s given, %s expected)
+ErrorPriceExpression8=Unexpected operator '%s'
+ErrorPriceExpression9=An unexpected error occured
+ErrorPriceExpression10=Iperator '%s' lacks operand
+ErrorPriceExpression11=Expecting '%s'
+ErrorPriceExpression14=Division by zero
+ErrorPriceExpression17=Undefined variable '%s'
+ErrorPriceExpression19=Expression not found
+ErrorPriceExpression20=Empty expression
+ErrorPriceExpression21=Empty result '%s'
+ErrorPriceExpression22=Negative result '%s'
+ErrorPriceExpressionInternal=Internal error '%s'
+ErrorPriceExpressionUnknown=Unknown error '%s'
 
 # Warnings
 WarningMandatorySetupNotComplete=Mandatory setup parameters are not yet defined
diff --git a/htdocs/langs/en_US/products.lang b/htdocs/langs/en_US/products.lang
old mode 100644
new mode 100755
index b38bcd150a9..f342ca57682
--- a/htdocs/langs/en_US/products.lang
+++ b/htdocs/langs/en_US/products.lang
@@ -242,3 +242,8 @@ ForceUpdateChildPriceSoc=Set same price on customer subsidiaries
 PriceByCustomerLog=Price by customer log
 MinimumPriceLimit=Minimum price can't be lower that %s
 MinimumRecommendedPrice=Minimum recommended price is : %s
+PriceExpressionEditor=Price expression editor
+PriceExpressionSelected=Selected price expression
+PriceExpressionEditorHelp="price = 2 + 2" or "2 + 2" for setting the price<br>ExtraFields are variables like "#options_myextrafieldkey# * 2"<br>There are special variables like "quantity" and "tva_tx"
+PriceMode=Price mode
+PriceNumeric=Number