英文一些詞性上轉換

1.何時to是當作介係詞呢?又何時當作不定詞!!?
介系詞的to是有文法功能及意義的，可形成片語，表示方向、終點、結果等，如：I want to talk to him. Count from one to ten. He was burnt to death. The score was six to one.後面會有一個名詞、動名詞、或代名詞等當其受詞。to出現在不定詞之前時，沒有文法功能（後面的字不是其受詞）及意義（不表方向等意義）。我們稱沒有to的不定詞為bare infinitive，有些時候必須使用bare infinitive。所以to只是一個不定詞的記號。

2.hope後面何時接to+原V何時直接加原V呢?
We hope to see you again soon.要用有to的不定詞當作及物動詞hope的受詞。
有些使役動詞和感官動詞後面的「受詞補語」使用bare infinitive，如:
Don't make me laugh!
I heard John knock at the door.
動詞hope好像沒有使用bare infinitive的狀況。

3.could can的用法差別
在直說語氣裡，could是can的過去式。
在假設語氣裡，我們只能用could，不用can。如：If I could go, I should be glad.；此外，could也可用在委婉語裡，The report could not be true.口氣較不武斷。Could you come and see me tomorrow?用could比用can客氣。

2015-07-27 20:29:51 補充：
「動名詞」只是可以當「介系詞」受詞當中的一種詞類，不是唯一的。

have got married to跟have been married to差別：
前者的主要動詞是get（連繫動詞），married是當作主詞補語。
I have got married to Jane.=我己跟Jane結婚了。

後者的主要動詞是be，married也是主詞補語。
I have been married to Jane.=我己跟Jane結婚了。

2015-07-28 10:33:16 補充：
have got是get的現在完成式
have been是be的現在完成式。

I have been married to Jane.也可以是：我曾經跟Jane結過婚（有可能現在她是別人的太太，我們離婚了。）。

2015-08-03 14:03:59 補充：
1.「介系詞」的功能用在原來沒有關係的兩個字之間。如兩個名詞之間，不及物動詞及受詞之間等。
2. 「現在完成式」的意義依action verbs與state verbs而不同。是action verbs時，發生在過去，但效果迄今猶存。be動詞則屬於state verb，表示以前曾經是這個狀況，但目前不含在內。所以才會有現在己離婚的可能。

自從失戀後,看到路上成雙成對,就格外放閃,嘴巴瀟灑說只是少一個人來愛,但不可否認還是希望可以多多認識新的朋友,
往認真爬文3個月以上,終於找到隱藏在網路中,傳說中的李姐,
在今年3月初就預約來找,果然是口碑相傳,不做廣告的,我排第3次就遇到雙方非常有感覺的,目前是暫停排約,
李姐那邊可以暫停排約1次,會員時間可以展延拉長時間,也在這段時間可以觀察對方.
推薦給有需要的朋友參考

(1)When is "to" act as a prep:-
---in the direction of; towards; walk to work; go to the tree; fall to the ground; off to usa; point to something; hold candle up to the light to see; on the way to the station;10 Km to Taipei city; going from city to city;
---use as towards a condition,quality,to reach the state of:-a tendency to lazy;, all to no purpose, to action, bring to tears,
---use with verbs of perception like:-seem; appear;feel; look; smell;touch

When is "to" act as an infinitive?
---used after many verbs, but not after can,do, may, must, shall He wants me to go;
---used with adv functions of purpose,result, outcome, :-They came to help. He lived to be eighty.--We make our iced-food to last.-ready to help;--easy to understand;--to go to school;-too hot to drink
---used with inf:-It is wrong to steal;---To err is human,-to forgive divine

(2)Hope as a noun:-feeling of expectation&desire,of trust&confidence:-eg:-There is not much hope they are alive;---hold out some hope of---not have a hope,;--raise somebody's hopesWe try to raise his hopes!!!!
---Hope vt.means expect and desire:-eg:-We hope to see you soon in President's Palace.--Will it be fine tomorrow?We hope so=fine .-Let us hope for the best. We've had no news from him in ussr,but we're still hoping.----hope against hope means only a mere possibility.---A pupil hopes to do well.----A young boy hopes to succeed---A manager manages to succeed.

(3)can/could indicating ability or capacity to do something,be able to; know how to;could is past tense;Okay ?Can you lift the heavy Box?She can't get the lid off. She can speak English.
---Could refers to ability or capacity in the past time;-eg:-She could read"ghost-image"when she was six.
---Could is used in if-clauses to indicate a condition,expressed or implied:-eg:-Could you lift the Box, if you tried?
---Impossible(conditional):-eg:-Main Clause=he could have passed-----IF Clause=If he had worked hard (=past perfect)