べんりだとおもいます
I think it's convenient
A noun, verb or adjective followed by と  おもう /と  おもいます  means ‘I think that .....’​
日本の  でんしゃ  は、とても  べんり  だ  と  おもいます。
  • I think Japan's trains are very convenient.
いぬ  だ  と  おもいます か。
  • Do you think it's a dog?
この  本  は、すごく  おもしろい  と  おもいます。
  • I think this book is very interesting.
THE GRAMMAR RULES FOR 'と おもいます'
PRESENT TENSE - 'I THINK (SOMETHING) IS/ISN'T ...'
  • NOUN FOLLOWED BY  'da to omoimasu'  OR 'ja nai to omoimasu'
​Remember, 'da' is the plain form of 'desu'. We often use the plain form inside complex grammar structures.
With the nouns いぬ (dog) and ひこうき (aeroplane)
​いぬ  だ と おもいます。  
  • I think it's a dog
​ひこうき じゃない と おもいます。
  • I think it's not an aeroplane. ( = I don't think it's an aeroplane.)
    Note that although in English we say 'I don't think (something) is...' , in Japanese we say 'I think (something) isn't ...
  • -NA ADJECTIVE FOLLOWED BY 'da to omoimasu' OR 'ja nai to omoimasu'
​Remember, -NA ADJECTIVES are actually noun forms that we can use as adjectives
With the な-adjective べんり  - convenient
​でんしゃ は べんり だ と おもいます
  • I think (that) trains are convenient
バス は べんり じゃない と おもいます
  • I think (that) buses are not convenient. ( = I do not think that buses are convenient.)
  • -i ADJECTIVE FOLLOWED DIRECTLY BY 'to omoimasu' OR '-ku nai to omoimasu'
​Remember, -い ADJECTIVES behave like verbs: they can take the past tense and can be changed into negative forms.
With the い-adjective おいしい  - delicious
おこのみやき は おいしい と おもいます
  • I think (that) okonomiyaki is delicious
やさい は おいしくない と おもいます
  • I think (that) vegetables are not delicious. ( = I do not think that vegetables are delicious.)
  • VERB  IN THE PLAIN FORM, FOLLOWED DIRECTLY BY 'to omoimasu'.​
​Remember, verbs can take the past tense and can be changed into negative forms.
With the verb ふる - to fall (from the sky)
あした、あめが  ふる  と  おもいます。
  • I think (that) it will rain tomorrow.
ゆき は  ふらない  と  おもいます。
  • I think (that) it will not snow. ( = I do not think it will snow.)