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#  Modules

LangChain provides standard, extendable interfaces and external integrations
for the following main modules:

####  [ Model I/O ](/docs/modules/model_io/) ​

Interface with language models

####  [ Retrieval ](/docs/modules/data_connection/) ​

Interface with application-specific data

####  [ Agents ](/docs/modules/agents/) ​

Let chains choose which tools to use given high-level directives

##  Additional  ​

####  [ Chains ](/docs/modules/chains/) ​

Common, building block compositions

####  [ Memory ](/docs/modules/memory/) ​

Persist application state between runs of a chain

####  [ Callbacks ](/docs/modules/callbacks/) ​

Log and stream intermediate steps of any chain

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