WHAT DOES THE PHRASE "faith as grain of mustard seed" MEANS?

Replying to the requirement of the apostles: "Increase our faith", Jesus said: " If you had faith as grain of mustard seed you could say to this sycamine tree , 'be rooted up and be planted in the sea' and it would obey you." 

How should we understand the phrase "faith as grain of mustard seed"?  can we measure the faith to know that how
large it is? of course we can not do that. we can know how small a mustard seed is. It is almost the smallest seed in comparison to the other kinds of seed. Therefore, What did Jesus means? Jesus imply that if you true faith, you can do every thing. 

The saying of the apostle 'increase my faith' proves that they have no faith at all. As we mentioned above, we cannot know the measurement of faith. What we can mention about our faith is that how true it is. In other words,  we believe or not. That's all. If we actually believe in God, we can do every great things as Jesus said. Actually, it is not we who can do great things but God himself does for us and we know that "with God all things are possible" (Mat. 19:26).

Nowadays, not many people have a a true faith. They can go to church, attend the Mass, and pray every day but they still live their daily life without God. For this reason, they cannot live a happy life and help their brothers and sisters live abundantly. That's a sad reality.

Jesus Christ, our Lord, Please help us so that we can believe in our God truly.

Thạch Phạm, SVD