diff --git a/ml/neural_network/neural_network.md b/ml/neural_network/neural_network.md
index ee1214b..d3d9d7f 100644
--- a/ml/neural_network/neural_network.md
+++ b/ml/neural_network/neural_network.md
@@ -75,7 +75,7 @@ $$
 
 神经网络是由多个层次的神经元组成的，每个层次含有数量可以是不相同的神经元，一个简单的神经网络结构如下图所示：
 
-![nn_model](images/nn_mode.jpg)
+![nn_model](images/nn_model.jpg)
 
 可以看到，任何一个神经网络，都包含一个**输入层**，一个**输出层**，以及若干数量不确定的**隐含层**(`hidden layer`)。输入层一般用$x$或者$a^{(1)}$来表示，其中$x_j$或者$a_j^{(1)}$表示第$j$个特征的值；第一个隐含层用$a^{(2)}$来表示，$a_j^{(2)}$表示第一个隐含层的第$j$个神经元的值，后面的隐含层以此类推；用$L$表示神经网络含有的层次数量，这样输出层就可以用$y$或者$a^{(L)}$来表示了。
 
@@ -126,7 +126,7 @@ $$
 &a^{(1)} = x\\\\
 &z^{(2)} = \Theta^{(1)}a^{(1)}, a^{(2)} = sigmoid(z^{(2)})\\\\
 &z^{(3)} = \Theta^{(2)}a^{(2)}, a^{(3)} = sigmoid(z^{(3)})\\\\
-&\cdots
+&\cdots\\\\
 &z^{(L)} = \Theta^{(L - 1)}a^{(L - 1)}, h_\Theta(x) = a^{(L)} = sigmoid(z^{L})
 \end{aligned}
 $$
@@ -147,7 +147,7 @@ $$
 
 如逻辑回归一样，神经网络也可以被推广到解决多分类问题，两者的方法如出一辙。对于逻辑回归而言，为了解决$n(n \ge 3)$分类问题，只需要训练$n$个二类分类问题的分类器即可；而对于神经网络模型，则只需要将输出层的神经元增加到$n$个，由于前面已经指出，神经网络的最后两个层次本质上就是逻辑回归模型，因此该方法本质上也是训练了$n$个二类分类器，与逻辑回归一致。多分类的神经网络结构如下所示：
 
-![nn_multiclass](images/nn_multicalss.jpg)
+![nn_multiclass](images/nn_multiclass.jpg)
 
 但是两者在实现的细节上也有一些差异。对于$n$类分类问题，逻辑回归的输出的取值往往是$\{1, 2, \cdots, n\}$，而神经网络则要沿用向量表示法，例如当$n = 3$时，神经网络的输出应该表示为
 
diff --git a/words.md b/words.md
index 0904f74..f02e0b3 100644
--- a/words.md
+++ b/words.md
@@ -2194,7 +2194,7 @@ Some Words
 	- Each store is owned by an individual who pays a fee for franchise.
 	- He lost the franchise after failing to meet the specified standards.
 
-##19th, January
+## 19th, January
 
 + wade
 > (v)to walk through water or other liquid with some effort, because it is deep enough to come quite high up your legs, or thick.
@@ -2219,6 +2219,40 @@ Some Words
 	- It was a clear day with little moisture in the air.
 	- Plants absorb carbon dioxide from the air and moisture from the soil.
 
+## 21st, February
+
++ ostensible
+> (adj)appearing or claiming to be one thing when it is really something else.
+
+	- Their ostensible goal was to clean up government corruption, but their real aim was to unseat the government.
+
++ supersede
+> (v)to relace something, especially something older or more old-fashioned.
+
+	- Most of the old roads have been superseded by the great interstate highways.
+	- Hand tools are relics of the past that have now been superseded by the machine.
+
++ disentangle
+> (v)to separate things that have become joined or confused.
+
+	- It's difficult to disentangle hard fact from myth, or truth from lies.
+	- I tried to disentangle the wires under my desk.
+
+## 23rd, February
+
++ commensurate
+> (adj)in a correct and suitable amount compared to something else.
+
+	- a salary that is commensurate with skills and experience
+	- The agency's workload has increased without any commensurate increase in staff.
+
+## 29th, February
+
++ efficacy
+> (n)the ability, especially of a medicine or a method of achieving something, to produce the intended result, effectiveness.
+
+	- They recently ran a series of tests to meausre the efficacy of the drug.
+
 + cosmetically
 + rationale
 + ameliorate