What is food security? What are its different dimensions?

Generally, food security means getting two square meals. But it has following dimesons:
(i) Availability of food: It implies food production within the country, food imports and the previous years stock stored in government granaries.
(ii) Accessibility: It means food is within the reach of every person.
(iii) Affordability : It implies that an individual has enough money to buy sufficient, safe and nutritious food to meet one’s dietary needs.