| Ocaml_operators | Precedence level and associativity of operators | 
| Format_tutorial | Principles | 
| CamlinternalFormatBasics | |
| CamlinternalAtomic | |
| Stdlib | The OCaml Standard library. | 
| Seq | Sequences (functional iterators). | 
| Option | Option values. | 
| Either | Either type. | 
| Result | Result values. | 
| Bool | Boolean values. | 
| Char | Character operations. | 
| Uchar | Unicode characters. | 
| Sys | System interface. | 
| List | List operations. | 
| Int | Integer values. | 
| Bytes | Byte sequence operations. | 
| String | Strings. | 
| Unit | Unit values. | 
| Marshal | Marshaling of data structures. | 
| Obj | Operations on internal representations of values. | 
| Array | Array operations. | 
| Float | Floating-point arithmetic. | 
| Int32 | 32-bit integers. | 
| Int64 | 64-bit integers. | 
| Nativeint | Processor-native integers. | 
| Lexing | The run-time library for lexers generated by  | 
| Parsing | The run-time library for parsers generated by  | 
| Set | Sets over ordered types. | 
| Map | Association tables over ordered types. | 
| Stack | Last-in first-out stacks. | 
| Queue | First-in first-out queues. | 
| CamlinternalLazy | Run-time support for lazy values. | 
| Lazy | Deferred computations. | 
| Stream | Streams and parsers. | 
| Buffer | Extensible buffers. | 
| CamlinternalFormat | |
| Printf | Formatted output functions. | 
| Arg | Parsing of command line arguments. | 
| Atomic | This module provides a purely sequential implementation of the concurrent atomic references provided by the Multicore OCaml standard library: | 
| Printexc | Facilities for printing exceptions and inspecting current call stack. | 
| Fun | Function manipulation. | 
| Gc | Memory management control and statistics; finalised values. | 
| Digest | MD5 message digest. | 
| Random | Pseudo-random number generators (PRNG). | 
| Hashtbl | Hash tables and hash functions. | 
| Weak | Arrays of weak pointers and hash sets of weak pointers. | 
| Format | Pretty-printing. | 
| Scanf | Formatted input functions. | 
| Callback | Registering OCaml values with the C runtime. | 
| CamlinternalOO | Run-time support for objects and classes. | 
| Oo | Operations on objects | 
| CamlinternalMod | Run-time support for recursive modules. | 
| Genlex | A generic lexical analyzer. | 
| Ephemeron | Ephemerons and weak hash tables. | 
| Filename | Operations on file names. | 
| Complex | Complex numbers. | 
| ArrayLabels | Array operations. | 
| ListLabels | List operations. | 
| BytesLabels | Byte sequence operations. | 
| StringLabels | Strings. | 
| MoreLabels | Extra labeled libraries. | 
| StdLabels | Standard labeled libraries. | 
| Bigarray | Large, multi-dimensional, numerical arrays. | 
| Dynlink | Dynamic loading of .cmo, .cma and .cmxs files. | 
| Str | Regular expressions and high-level string processing | 
| Unix | Interface to the Unix system. | 
| UnixLabels | Interface to the Unix system. | 
| Thread | Lightweight threads for Posix  | 
| Condition | Condition variables to synchronize between threads. | 
| Mutex | Locks for mutual exclusion. | 
| Event | First-class synchronous communication. | 
| ThreadUnix | Thread-compatible system calls. | 
| Semaphore | Semaphores |