strstr

if(strstr(sent, word) != NULL) {
    /* ... */
}

#include <iostream>
#include <cstring>
using namespace std;
  
int main()
{
    char s1[10] = "Hello";
  
    // return length of s1
    cout << strlen(s1) << endl;
  
    char s2[50];
  
    // copies s1 into s2
    strcpy(s2, s1);
    cout << s2 << endl;
  
    char s3[10] = "World";
  
    // concatenates s3 into s2
    strcat(s2, s3);
    cout << s2 << endl;
  
    char s4[50] = "HelloWorld";
  
    // return 0 if s2 and s4 are equal.
    if (strcmp(s2, s4) == 0)
        cout << "true" << endl;
    else
        cout << "false" << endl;
  
    char s5[30];
  
    // copies first 5 chars of s2 into s1
    strncpy(s5, s4, 5);
    cout << s5 << endl;
  
    char target[10] = "Hello";
  
    // search for target string in s4
    if (strstr(s4, target) != NULL)
        cout << "true" << endl;
    else
        cout << "false" << endl;
  
    return 0;
}

5
Hello
HelloWorld
true
Hello
true