op-guide: fix monitor typos (#652)

Author: lilin90

op-guide/monitor-overview.md

@@ -10,7 +10,7 @@ The TiDB monitoring framework adopts two open source projects: Prometheus and Gr
 
 ## About Prometheus in TiDB
 
-As a time series database, Prometheus has a multi-dimensional data model and flexible query language. As one of the most popular open source projects, many companies and organizations have adopted Prometheus, and the project has a very active community. PingCAP is one of the active developers and adoptors of Prometheus for monitoring and alerting in TiDB, TiKV and PD.
+As a time series database, Prometheus has a multi-dimensional data model and flexible query language. As one of the most popular open source projects, many companies and organizations have adopted Prometheus, and the project has a very active community. PingCAP is one of the active developers and adopters of Prometheus for monitoring and alerting in TiDB, TiKV and PD.
 
 Prometheus consists of multiple components. Currently, TiDB uses the following of them:
 
@@ -24,6 +24,6 @@ The diagram is as follows:
 <img src="../media/prometheus-in-tidb.png" width="500">
 
 ## About Grafana in TiDB
-Grafana is an open source project for analysing and visualizing metrics. TiDB uses Grafana to display the performance metrics as follows:
+Grafana is an open source project for analyzing and visualizing metrics. TiDB uses Grafana to display the performance metrics as follows:
 
 ![screenshot](../media/grafana-screenshot.png)

op-guide/monitor.md

@@ -46,7 +46,7 @@ The default port number is: 2379.
 
 See [PD API doc](https://cdn.rawgit.com/pingcap/docs/master/op-guide/pd-api-v1.html) for detailed information about various API names.
 
-The interface can be used to get the state of all the TiKV servers and the information about load balancing. It is the most important and frequently-used interface to get the state information of all the TiKV nodes. See the following example for the the information about a single-node TiKV cluster:
+The interface can be used to get the state of all the TiKV servers and the information about load balancing. It is the most important and frequently-used interface to get the state information of all the TiKV nodes. See the following example for the information about a single-node TiKV cluster:
 
 ```bash
 curl http://127.0.0.1:2379/pd/api/v1/stores
@@ -155,7 +155,7 @@ See the following links for your reference:
     - Set the Push Gateway address as the `--metrics-addr` parameter.
     - Set the push frequency as the `--metrics-interval` parameter. The unit is s, and the default value is 15.
 
-+ PD: update the toml configuration file with the Push Gateway address and the the push frequency:
++ PD: update the toml configuration file with the Push Gateway address and the push frequency:
 
     ```toml
     [metric]