diff --git a/README.md b/README.md
index 0bb62d538f5..06f0e08720b 100644
--- a/README.md
+++ b/README.md
@@ -28,7 +28,7 @@ instructions.
 ## Documentation
 
 For a quick start, to access the distribution and API documentation of
-OPAM packages do:
+opam packages do:
 
 ```
 odig ocamldoc
diff --git a/SEL.md b/SEL.md
index d80fb0a269c..fb05b0aa79d 100644
--- a/SEL.md
+++ b/SEL.md
@@ -58,7 +58,7 @@ x-odig-sel-$SEL:
 ```
 
 * `$SEL` the selector to which it applies (the toplevel package name
-   can be replaced by `_` following OPAM conventions).
+   can be replaced by `_` following opam conventions).
 * `$QUERY`
   `{compile,link,dynlink}-{flags,files,deps}-{byte,native}-{pre,post,replace}`
    or maybe give more structure to the subfield.
diff --git a/etc/odig.conf b/etc/odig.conf
index 9ddea14b6c5..62f546eb639 100644
--- a/etc/odig.conf
+++ b/etc/odig.conf
@@ -1 +1 @@
-opam ;; Mine current OPAM switch
+opam ;; Mine current opam switch
diff --git a/src-bin/distrib_doc.ml b/src-bin/distrib_doc.ml
index 90005239b97..017854ab65d 100644
--- a/src-bin/distrib_doc.ml
+++ b/src-bin/distrib_doc.ml
@@ -126,7 +126,7 @@ let changes_cmd =
   cmd "changes" ~kind:"change log" ~get:Pkg.change_logs
 
 let tag =
-  let doc = "Read license tags from the package's OPAM file. Implies
+  let doc = "Read license tags from the package's opam file. Implies
              $(b,--no-pager)."
   in
   Arg.(value & flag & info ["t"; "tag"] ~doc)
diff --git a/src-bin/help.ml b/src-bin/help.ml
index ec40eeb0abb..6e19dd3b3ca 100644
--- a/src-bin/help.ml
+++ b/src-bin/help.ml
@@ -28,7 +28,7 @@ let basics =
     `Pre " odig readme bos";`Noblank;
     `Pre " odig changes bos";`Noblank;
     `Pre " odig license bos";
-    `P "If the package properly installed its OPAM metadata file you can
+    `P "If the package properly installed its opam metadata file you can
         also quickly get access to the issues, homepage, or
         online documentation pages of a package. The following commands
         opens them in your browser:";
@@ -71,7 +71,7 @@ let packaging =
         called $(i,LIBDIR) and have their distribution documentation installed
         in a library prefix called $(i,DOCDIR).";
     `P "For a package named $(i,PKG) to be recognized by odig $(i,PKG)
-        must be a valid OPAM package name and one of the following paths
+        must be a valid opam package name and one of the following paths
         must exist:";
     `P "$(i,LIBDIR)/$(i,PKG)/opam";`Noblank;
     `P "$(i,LIBDIR)/$(i,PKG)/META"; `Noblank;
@@ -83,11 +83,11 @@ let packaging =
         $(i,DOCDIR)/$(i,PKG).";
     `P "Typically the values of $(i,LIBDIR) and $(i,DOCDIR) will
         be `opam config var lib` and `opam config var doc`. However
-        odig is not tied to OPAM, the only assumption made by odig is
+        odig is not tied to opam, the only assumption made by odig is
         that the above install structure is followed.";
     `S "METADATA RECOGNITION";
     `P "Package metadata for $(i,PKG) is always read from
-        $(i,LIBDIR)/$(i,PKG)/opam which must be a valid OPAM
+        $(i,LIBDIR)/$(i,PKG)/opam which must be a valid opam
         file. If present, the following fields are consulted and used
         by odig in various context and/or commands.";
     `I ("authors:", "The authors, $(b,authors) command");
diff --git a/src/odig.mli b/src/odig.mli
index 84d891d604a..e397214396e 100644
--- a/src/odig.mli
+++ b/src/odig.mli
@@ -818,14 +818,14 @@ module Pkg : sig
   val conf : t -> Conf.t
   (** [conf p] is the configuration in which [p] was found. *)
 
-  (** {1 Package metadata (OPAM file)} *)
+  (** {1 Package metadata (opam file)} *)
 
   val opam_file : t -> Fpath.t
-  (** [opam_file p] is [p]'s expected OPAM file path. *)
+  (** [opam_file p] is [p]'s expected opam file path. *)
 
   val opam_fields :
     t -> (string list Astring.String.map, [`Msg of string]) result
-  (** [opam_fields p] is the package's OPAM fields. This is
+  (** [opam_fields p] is the package's opam fields. This is
       {!String.Set.empty} [opam_file p] does not exist. *)
 
   val license_tags : t -> (string list, [`Msg of string]) result
@@ -856,11 +856,11 @@ module Pkg : sig
   (** [repo p] is [p]'s [dev-repo:] field. *)
 
   val deps : ?opts:bool -> t -> (Astring.String.set, [`Msg of string]) result
-  (** [deps p] are [p]'s OPAM dependencies if [opt] is [true]
+  (** [deps p] are [p]'s opam dependencies if [opt] is [true]
       (default) includes optional dependencies. *)
 
   val depopts : t -> (Astring.String.set, [`Msg of string]) result
-  (** [deps p] are [p]'s OPAM optional dependencies. *)
+  (** [deps p] are [p]'s opam optional dependencies. *)
 
   (** {1 Standard distribution documentation}
 
diff --git a/src/odig_opam.ml b/src/odig_opam.ml
index 63596f2c7d4..4e77aeded4c 100644
--- a/src/odig_opam.ml
+++ b/src/odig_opam.ml
@@ -61,12 +61,12 @@ module File = struct
       (* FIXME add OpamFile.OPAM.extensions when supported *)
       known_fields
     in
-    Logs.info (fun m -> m "Parsing OPAM file %a" Fpath.pp file);
+    Logs.info (fun m -> m "Parsing opam file %a" Fpath.pp file);
     try Ok (parse file) with
     | exn ->
         (* Apparently in at least opam-lib 1.2.2, the error will be logged
              on stdout. *)
-        R.error_msgf "%a: could not parse OPAM file" Fpath.pp file
+        R.error_msgf "%a: could not parse opam file" Fpath.pp file
 
   let deps ?(opts = true) fields =
     let deps = match String.Map.find "depends" fields with
diff --git a/src/odig_opam.mli b/src/odig_opam.mli
index ec92d4375e1..7793c7a4427 100644
--- a/src/odig_opam.mli
+++ b/src/odig_opam.mli
@@ -4,9 +4,9 @@
    %%NAME%% %%VERSION%%
   ---------------------------------------------------------------------------*)
 
-(** OPAM interaction. *)
+(** opam interaction. *)
 
-(** {1 OPAM} *)
+(** {1 opam} *)
 
 open Bos_setup
 
diff --git a/src/odig_pkg.ml b/src/odig_pkg.ml
index a5e5fa54059..5ed962bdd7a 100644
--- a/src/odig_pkg.ml
+++ b/src/odig_pkg.ml
@@ -187,7 +187,7 @@ let _cache p =
 let cobjs_trail p = fst (Lazy.force p.cache)
 let cobjs p = snd (Lazy.force p.cache)
 
-(* OPAM file and fields *)
+(* opam file and fields *)
 
 let pkg_opam_fields conf name =
   let opam_file = pkg_opam_file conf name in
@@ -259,7 +259,7 @@ let conf_cobj_index c = try Hashtbl.find memo c with
     Hashtbl.add memo c i;
     i
 
-(* OPAM *)
+(* opam *)
 
 let opam_file p = pkg_opam_file p.conf p.name
 let opam_fields p = Lazy.force p.opam_fields